- The connection between your thyroid and fertility
- First… a refresher on thyroid disorders
- Thyroid dysfunction and reproductive health
- “Normal range” TSH levels and unexplained fertility problems
- What about thyroid dysfunction and male fertility?
- Your thyroid while you’re pregnant
- Treatments for thyroid disorders
- So, what’s the bottom line with all this?
- Hyperthyroidism and fertility
- Why does the thyroid matter in fertility?
- Thyroid hormone levels
- Thyroid antibodies
- Preventative measures
- How does a thyroid affect fertility?
- What thyroid disorders are most commonly associated with fertility?
- Are there other infertility issues that are associated with thyroid problems?
- Can thyroid disorders hurt male fertility too?
- How do I know that I have a thyroid problem?
- What can be done to fix a thyroid problem?
- Is there anything I can do on my own?
- How long does it take to resolve thyroid issues?
- If I have infertility due to thyroid issues, what treatment will I need?
- Are there any special considerations I should take during pregnancy?
- Hypothyroidism and Pregnancy: What Should I Know?
- What is hypothyroidism?
- What does the thyroid gland do?
- What are the symptoms of hypothyroidism?
- What causes hypothyroidism?
- How is hypothyroidism tested?
- How does hypothyroidism affect my fertility and my baby if I become pregnant?
- How is hypothyroidism treated?
- Do I need to continue to monitor my thyroid levels?
- Borderline Thyroid Deficiency Linked to Female Infertility
- Trying to get pregnant with Hashimoto’s and an underactive thyroid
The connection between your thyroid and fertility
The thyroid is a small gland located in your neck. Its job, as a crucial part of the endocrine system, is to control your body’s metabolism — the process by which your body converts what you eat and drink into energy — through the hormones it releases. The thyroid gets a message from the pituitary gland via thyroid-stimulating hormone (TSH) and releases triiodothyronine (T3), thyroxine (T4), and calcitonin.
While many are aware that an imbalance of TSH, T3, and T4 can cause weight or mood changes, did you know that it can also impact your menstrual cycle and fertility? In other words, your thyroid is something that’s worth paying attention to.
Keep reading to find out the answers to the following questions:
- What are thyroid disorders?
- How is thyroid dysfunction related to fertility?
- Can thyroid dysfunction impact male fertility?
- What can happen if you get pregnant with a thyroid disorder?
- How can you minimize the risk of thyroid-related fertility issues?
First… a refresher on thyroid disorders
Thyroid disease is much more common in women than men — about five to eight times more common (the medical community is still not really sure why this is the case).
Hyperthyroidism (high levels of thyroid hormones due to an overactive thyroid gland) affects up to 5% of women. Symptoms of this condition can include unexplained weight loss, increased appetite, feelings of nervousness and anxiety, difficulty sleeping, fewer or lighter menstrual cycles, increased sweating, and heat intolerance.
Hypothyroidism (low levels of thyroid hormones due to an underactive thyroid gland) is found in 2-4% of women. Some common symptoms seen in hypothyroidism are weight gain, fatigue, constipation, feeling cold, thinning hair, pale skin, and increased or heavier menstrual bleeding. (Because of the similarity in symptoms between hypothyroidism and polycystic ovarian syndrome, or PCOS, providers will often check thyroid hormones when evaluating patients for PCOS, and vice versa.)
Proactive screening of thyroid hormone levels through a blood test is not currently routinely performed by doctors on nonpregnant women of reproductive age who aren’t experiencing symptoms. (Though the American Thyroid Association recommends looking into thyroid function regularly starting at age 35.) But if you have a family history of thyroid dysfunction, a personal or familial history of autoimmune disease (which can be related to thyroid function), or are suffering from symptoms of hypothyroidism or hyperthyroidism, it’s important to get your thyroid checked out.
If you’re wondering about your thyroid hormones — because you’re dealing with related symptoms or simply out of curiosity — we’ve got your back. With the Modern Fertility test, you can measure your TSH levels, among other reproductive hormones.
Thyroid dysfunction and reproductive health
Thyroid function is regulated by the hypothalamus-pituitary axis (HPA), an interconnected duo made up of the hypothalamus (a part of the brain that produces hormones) and the pituitary gland (which waits for its cue from the hypothalamus). This pair is as thick as thieves — when one of these organs sends a signal, it sets off a chain reaction in the other.
Because the HPA also controls the production of some of the most important hormones related to fertility, thyroid dysfunction can impact how much of those hormones are released. When any of these deviations from the status quo happen, they can disrupt (or stop) menstrual cycles. Without the complete cycle, including ovulation, fertilization, and implantation, you can’t get pregnant naturally.
As a result of these hormone changes, both hyperthyroidism and hypothyroidism have been linked to abnormal menstrual cycles. (Several studies point to prolactin as the main driver in this.)
All that said, getting a handle on your thyroid through treatment can reduce the chances of related fertility issues down the line. In one study of a group of almost 400 women suffering from infertility, 24% of participants were found to have hypothyroidism — but within a year of treatment, 76% were able to conceive. (The power of medicine!)
“Normal range” TSH levels and unexplained fertility problems
In one study conducted between 2000 and 2012, women with unexplained infertility were found to have TSH levels on the higher end of “normal” than the control population — which is indicative of subclinical (read: mild) thyroid disorder, though not of full-blown hypothyroidism.
What this means: Even less-dramatically elevated, within-range levels of TSH can result in difficulty conceiving. (All the more reason to check in with your levels and get ahead of any issues.)
What about thyroid dysfunction and male fertility?
An impaired thyroid doesn’t just have the power to impact women’s ability to conceive — there’s also an effect on male fertility. Why? Because T3 and T4 both play a role in the development and function of the testes.
Hyperthyroidism can lead to reductions in:
- Semen volume, or how much is ejaculated
- Sperm density, or the sperm count per milliliter of semen
- Sperm motility, or how well and efficiently the sperm move
- Sperm morphology, or the size and shape of sperm
Hypothyroidism can lead to reduction in:
- Sperm morphology
Just like the effects of thyroid dysfunction on people with ovaries, people with testes can reverse thyroid-related fertility issues once the gland is back in working order after treatment.
Your thyroid while you’re pregnant
There are a few ways pregnancy can be impacted if thyroid problems aren’t addressed first.
Increasing demands from a developing baby can occasionally cause new onset or worsening hypothyroidism for pregnant women.
Additionally, impaired thyroid function (due to diagnosed conditions and/or the presence of thyroid antibodies) prior to and during conception can impact healthy brain development in the fetus. That said, T4 therapy through meds like levothyroxine can decrease the risk of babies born with a lower body weight and other complications.
As for pregnancy loss and miscarriage, there’s been little evidence found to directly link hyperthyroidism (in the absence of autoimmune thyroid disorder, or AITD) to either. But one study did find that the risk of miscarriage is doubled with hyperthyroid women as compared to women without thyroid issues. (This is likely due to excess thyroid hormones toxically affecting the development of embryos.) In terms of hypothyroidism (overt or sublinical), there is evidence that suggests that inadequate treatment can lead to infertility, miscarriage, and adverse pregnancy outcomes.
After pregnancy, there’s also an increased risk for postpartum thyroiditis, or inflammation of the thyroid — this happens to five to ten out of every 100 women within the first year after childbirth. This can lead to temporary (lasting up to a year) hypothyroidism, hyperthyroidism, or hyperthyroidism followed by hypothyroidism.
Treatments for thyroid disorders
Treating thyroid disorders before trying to have kids can decrease the risk for any issues impacting your ability to get pregnant or have a successful pregnancy. The treatments for hyperthyroidism and hypothyroidism vary depending on severity of symptoms and provider preference, but they can often be treated with medications prescribed by your doctor.
Typically, patients will be under close surveillance with initial treatment (labs drawn every six weeks to a few months) until a proper maintenance dose can be picked. Once a patient has a maintenance dose, thyroid labs will still need to be checked on a yearly basis.
Well, for starters, even though the thyroid is a pretty tiny gland, it’s important. Because it isn’t always checked regularly, being aware of the symptoms of thyroid imbalance can be incredibly useful. If your periods are irregular or you’re experiencing something unusual that resembles any of the above symptoms, pay a visit to your doctor. They can help you get to the bottom of it and treat the problem before it makes getting pregnant more difficult.
Last but not least: If all of this has got you thinking about your own thyroid levels, or your fertility as a whole, take the Modern Fertility test to complete a few pieces of the reproduction puzzle. Because even teeny glands like the thyroid and short, three-letter acronyms like TSH can give you a big-picture perspective of your health. (Talk about powerful.)
For more info, you can watch our Q&A with Dr. Cindy Duke below.
This article was medically reviewed by Dr. Eva Marie Luo, an OB-GYN at Beth Israel Deaconess Medical Center and a Health Policy and Management Fellow at Harvard Medical Faculty Physicians, the physicians organization affiliated with the Beth Israel-Lahey Health System.
MONDAY, Jan. 26, 2015 (HealthDay News) — A new study supports the notion that thyroid disorders can cause significant reproductive problems for women.
The report’s authors believe that testing for thyroid disease should be considered for women who have fertility problems and repeated early pregnancy loss.
The research, published Jan. 23 in The Obstetrician & Gynaecologist, found that 2.3 percent of women with fertility problems had an overactive thyroid (hyperthyroidism), compared with 1.5 percent of those in the general population. The condition is also linked with menstrual irregularity, the researchers said.
“Abnormalities in thyroid function can have an adverse effect on reproductive health and result in reduced rates of conception, increased miscarriage risk and adverse pregnancy and neonatal outcomes,” said study co-author Amanda Jefferys in a journal news release. She is a researcher from the Bristol Center for Reproductive Medicine at Southmead Hospital in Bristol, England.
While the study couldn’t prove cause-and-effect, one expert in the United States said he wasn’t surprised by the findings.
“For over two decades now, we have noticed a strong link between hypo- and hyperthyroidism and infertility as well as adverse pregnancy and neonatal outcomes,” said Dr. Tomer Singer, a reproductive endocrinologist at Lenox Hill Hospital in New York City.
“I support routine screening of the general population for thyroid dysfunction at the start of pregnancy and especially when seeking fertility treatment or struggling with miscarries,” he added.
The thyroid produces hormones that play key roles in growth and development. According to the British researchers, changes in thyroid function can have a major effect on reproductive function before, during and after conception.
Hypothyroidism (underactive thyroid) affects about 0.5 percent of women of reproductive age. In children and teens, the condition is associated with a delay in reaching sexual maturity, according to the researchers.
In adult women, hypothyroidism is linked with menstrual problems and a lack of ovulation in some cases, the new study found.
The researchers also noted that thyroid disease is associated with an increased risk of problems during pregnancy, including miscarriage, preeclampsia, poor fetal growth, premature birth and stillbirth.
Hyperthyroidism and fertility
Why does the thyroid matter in fertility?
The thyroid is an endocrine gland which produces hormones that regulate the growth and function of other bodily systems. It is crucial for regulating metabolism, energy production, oxygen utilisation and hormone levels.
Thyroid hormones are produced by everybody, and play an important part in growth. As such they are critical in pregnancy. If the thyroid is over or underactive, this can affect ovulation regulation and reduce fertility. Many women suffer from thyroid dysfunction; around 25% of women in their lifetime, which is around 4x more women than men. Graves disease is the most common thyroid dysfunction, affecting 1% of the population. These conditions are important in fertility, because thyroid hormones are important in regulating ovulation, preventing miscarriage and aiding foetal brain development.
Thyroid hormone levels
Thyroid hormone levels can be measured by a simple thyroid stimulating hormone (TSH) blood test. It is important that TSH is at an optimal level, as it affects ovulation; up to 5% of women struggling to conceive have abnormal thyroid hormone levels. Thyroid hormone levels are also important in the development of the foetus, as they are crucial in growth. It has been found that children have higher IQs when expectant mothers are screened for thyroid stimulating hormone (TSH) levels, as potential thyroid dysfunctions are picked up and treated. The best way to assess thyroid levels is to ask for a blood test. Conventional wisdom suggests that 4.2 should be the upper limit for TSH. However, recent studies have suggested that TSH should be no higher than 2.5 when trying to conceive and 3.0 during pregnancy. Thyroid hormones are synthesised from iodine, so it is also important that iodine levels are optimal. If TSH or iodine levels prove to be too high/low, this can be easily rectified with supplementary medication.
Hyperthyroidism: Hyperthyroidism is when the thyroid is overactive and produces excess amounts of thyroid hormones. Graves disease and other autoimmune diseases are the most common manifestations of this. The presence of hyperthyroidism can be measured by performing a TSH blood test. Hyperthyroidism can cause infrequent periods in women and low sperm counts in men. Once hyperthyroidism has been diagnosed it can be treated with medication, radioactive iodine or surgery, after which hormone levels generally return to normal.
Hypothyroidism: Hypothyroidism occurs when the thyroid is underactive and does not produce enough thyroid hormones. This is often caused by a lack of iodine in the diet, or by autoimmune diseases such as Hasimoto’s thyroiditis. It is associated with reduced fertility, an increased risk of miscarriage, lower infant intelligence, pre-eclampsia, premature birth and infant death. Hypothyroidism can again be diagnosed with a simple blood test. Treatment is usually supplementation with iodine or a synthetic form of thyroid hormone, thyroxine.
As well as levels of thyroid hormones, thyroid antibodies are another factor which has an impact on fertility. These are produced if the thyroid is being mistakenly attacked by the immune system as part of an auto-immune disease, and they are present in between 8 and 30% of infertile women. The presence of thyroid antibodies increases the risk of pregnancy loss, making it about 4x more likely. The mechanism of this is not yet clear; it could affect implantation or interact with other antibodies. Again, the best way to pick up on this is to undergo a blood test, so that appropriate treatment can be arranged if necessary.
Apart from diagnosis and medication, there are some lifestyle choices that can be taken to ensure that the thyroid functions properly. Reducing stress is important, as high cortisol (a stress hormone) levels inhibit thyroid hormone production. Increasing exercise is also helpful, as it promotes the production of thyroid hormones and increases the sensitivity of the tissues to these hormones. Modern diets also play a large part in thyroid dysfunction, in particular refined grains, sugars, soy products, peanuts and caffeine. Eating a healthy diet and avoiding smoking and alcohol consumption are therefore recommended.
We asked Dr. Chris Sipe, President and Physician at Fertility Centers of Illinois, the 10 most common questions he hears about how thyroid disorders affect fertility:
How does a thyroid affect fertility?
Located in the front of the neck, the butterfly-shaped gland known as the thyroid works in response to the pituitary gland within the endocrine system. The main function of both is to produce and regulate hormones. The pituitary gland in your brain creates thyroid-stimulating hormone (TSH) which triggers the thyroid to produce two other hormones, T3 and T4. When T3 and T4 production is high or low, thyroid issues can result. Those thyroid imbalances can create fertility issues. This can cause an increased rate of pregnancy loss, ovulatory disorders, irregular periods, preterm birth and lower IQs.
What thyroid disorders are most commonly associated with fertility?
Doctors look for abnormalities in hormone levels, which typically result in a diagnosis of hyperthyroidism or hypothyroidism. Hyperthyroidism occurs when the thyroid overproduces hormones. Patients may suffer from anxiety, tremors, rapid heart rate, weight loss, more frequent bowel movements, intolerance to heat, and brittle hair. Infertility symptoms can include loss of libido and menstrual cycle irregularities. Hypothyroidism occurs when the thyroid under-produces hormones. Common symptoms include fatigue, low energy, muscle weakness, weight gain, depression, constipation, intolerance to cold, and dry skin. Infertility symptoms can include menstrual cycle abnormalities with cycles being heavier and less frequent, a low Basal Body Temperature and difficulty conceiving. As you can see, some of these signs can be indicative of other fertility problems, making symptoms a challenge to assess.
Are there other infertility issues that are associated with thyroid problems?
Thyroid issues are also commonly diagnosed alongside Polycystic Ovarian Syndrome (PCOS) as both involve abnormal hormone levels. For women who receive a dual diagnosis, do not despair – balancing the hormones leads to significantly improved chances when trying to have a baby.
Can thyroid disorders hurt male fertility too?
Hypothyroidism in men can lead to a variety of fertility issues – reduced sperm volume and motility (movement), sperm defects, a lower libido, problems sustaining an erection, and lowered male fertility hormones such as testosterone, luteinizing hormone (LH) and follicle stimulating hormone (FSH). If thyroid issues are suspected, it is best to run a complete thyroid panel.
How do I know that I have a thyroid problem?
A simple blood test with your physician can assess TSH levels. Normal TSH levels fall between 0.5 to 4.5, with higher levels being associated with hyperthyroidism and lower levels associated with hypothyroidism. Should hormone levels fall outside normal ranges, your physician will also test your T4 to assess further.
What can be done to fix a thyroid problem?
For people with hypothyroidism, physicians will prescribe the missing hormone to correct the low levels. Levothyroxine (Synthroid) is the medicine most commonly prescribed to correct the problem. Patients can suffer a myriad of symptoms while their thyroid levels equilibrate, but most will feel their symptoms resolve. Levothyroxine has no major side effects on its own. Hyperthyroidism is a more complex endocrine problem to treat. Options include medication like methimazole and propylthiouracil, surgery to remove the thyroid and radioactive iodine, amongst other modalities.
Is there anything I can do on my own?
Living a healthy lifestyle always supports fertility. Excess weight can contribute to hormonal imbalances, throwing ovulation off in women and hormone balance off in men as well. Exercise regularly, keep stress low, stay away from cigarettes and marijuana, limit alcohol to no more than a drink per day, and limit caffeine to two servings per day. A healthy diet rich in iodine, whole grains, veggies and lean protein can also help. Iodine-rich foods can include navy beans, strawberries, whole fat yogurt, raw cranberry, dried seaweed, cod fish, tuna, and turkey breast. Your physician may also recommend natural supplements such as Zinc, Vitamin E, Vitamin A, Vitamin B and Vitamin C.
How long does it take to resolve thyroid issues?
This will depend upon how much hormone levels are imbalanced as well as if there are any other medical issues present. For moderate thyroid issues that do not involve an additional medical diagnosis, hormone levels can commonly be restored within a few months.
If I have infertility due to thyroid issues, what treatment will I need?
Before any fertility treatment can be prescribed, thyroid hormone levels must be brought into balance. For some, this is all of the treatment that will be required as natural conception may occur once the thyroid is functioning normally.
Are there any special considerations I should take during pregnancy?
If you are placed on levothyroxine, there are few risks to the pregnancy, but your required dose generally increases during pregnancy. For hyperthyroid medications, there are documented birth defects that can be associated with their use, so consultation with a maternal-fetal medicine physician should occur prior to pregnancy. It will be important to be monitored closely and regularly by your doctor during your pregnancy. You may have a higher risk of pregnancy loss with hypothyroidism, while hyperthyroidism is known to cause pre-term labor issues and low birth weight. The diagnosis of a thyroid issue does not mean this will occur as many women with thyroid issues give birth to healthy babies, but it is important to have regular physician visits and monitoring.
Hypothyroidism and Pregnancy: What Should I Know?
What is hypothyroidism?
Hypothyroidism (underactive thyroid) is when the thyroid gland produces less thyroid hormone than it should. The thyroid gland is found in the lower part of the throat and partially wraps around the upper windpipe (trachea).
What does the thyroid gland do?
The thyroid gland produces two hormones: triiodothyronine (T3) and thyroxine (T4). These hormones play an important role in metabolism. Metabolism is the body’s ability to transform food into energy. The thyroid gland is controlled (regulated) by thyroid-stimulating hormone (TSH). TSH is produced by the pituitary gland, which is located in the brain.
What are the symptoms of hypothyroidism?
When the thyroid gland produces less thyroid hormone than it should (hypothyroidism), metabolism slows down and causes a variety of symptoms. At first, the symptoms of hypothyroidism may not be noticed, but over time these symptoms may become more obvious and severe and can include the following:
- Fatigue (feeling tired)
- Weight gain
- Irregular periods
- Loss of sex drive
- Hair loss
- Brittle hair and nails
- Dry, itchy skin
- Difficulty learning and remembering
- Repeated miscarriage
What causes hypothyroidism?
The most common cause of hypothyroidism is an autoimmune disorder called Hashimoto’s thyroiditis. The body’s immune system mistakenly sends out antibodies to destroy the cells in the thyroid gland. This may cause the thyroid gland to enlarge, known as goiter.
Hypothyroidism and goiter can also result from not getting enough iodine in your diet. Hypothyroidism also can occur after thyroid surgery or radioactive iodine therapy given to treat hyperthyroidism. In many cases, the specific cause of hypothyroidism is not known.
How is hypothyroidism tested?
The main test used to detect hypothyroidism is measuring blood levels of TSH. An elevated TSH level usually means the thyroid gland is not making enough thyroid hormone, and the pituitary gland has responded by making more TSH to try to get the thyroid hormone levels where they should be.
Other blood tests include measuring T4 and thyroid autoantibodies. Antibodies are substances made by your immune system, usually to protect you against bacterial and viral infections. Sometimes, however, the immune system can make antibodies against your own body—such as against your thyroid. T4 is a hormone produced directly by the thyroid gland. It is typically low in patients with hypothyroidism. An autoantibody is an antibody that attacks the cells and tissues of the organism that made it. Thyroid autoantibodies are seen in patients with Hashimoto’s (autoimmune) thyroiditis.
How does hypothyroidism affect my fertility and my baby if I become pregnant?
Hypothyroidism can prevent the release of the egg from the ovary (ovulation). Typically, for women who have periods (menstruate) each month, an egg is released from the ovary each month. But women who have hypothyroidism may release an egg less frequently or not at all.
Hypothyroidism can also interfere with the development of an embryo (fertilized egg). This increases the risk of miscarriage. Also, if you are pregnant and your hypothyroidism is not treated, your baby may be born prematurely (before the predicted due date), weigh less than normal, and have lowered mental capacity.
It is very important for patients to have their thyroid hormones checked and receive appropriate treatment if they wish to have a baby or are already pregnant.
How is hypothyroidism treated?
The most commonly used medication to treat hypothyroidism is called levothyroxine. Levothyroxine is a tablet that is usually taken once a day. Once you start taking levothyroxine, you should have your blood checked in 4–6 weeks to measure the level of thyroxine and to make sure you are taking the right dose.
Do I need to continue to monitor my thyroid levels?
It is important to have blood levels checked regularly even after the correct dose is found. Hypothyroidism is often a lifelong and progressive disease and the dose of thyroid hormone replacement may need adjustment.
Frequent monitoring is important; if the dose of thyroid replacement hormone is too high, women may develop treatment-induced hyperthyroidism. This could cause heart palpitations, nervousness, and osteoporosis (bone loss and bone thinning).
If you become pregnant, your doctor will need to monitor your blood every trimester as your levothyroxine dose needs may change due to pregnancy.
Borderline Thyroid Deficiency Linked to Female Infertility
With Pouneh K. Fazeli, MD, and Tamara Wexler, MD, PhD
Subclinical hypothyroidism may have an association with unexplained infertility in women, according to a team of researchers from Harvard Medical School who believe the finding could point to an “economical first step” in treating people trying to conceive.1
“We were surprised by the strength of the association. Importantly, our results held up even after controlling for variables that may affect TSH levels including body mass index (BMI) and age,” Pouneh K. Fazeli, MD, a neuroendocrinologist at Harvard Medical School, and senior author told EndocrineWeb.
“I think the strength of our study was the fact that our population was very carefully selected. We did not include anyone with a history of abnormal levels of thyroid-stimulating hormone (TSH) and all of the patients included in our study had normal fertility evaluations, except that patients in the control group had a male partner with a very low sperm count,” Dr. Fazeli said.
Slight Drop in Thyroid Level May Impact Fertility
Although previous work has linked severe hypothyroidism to difficulty in conceiving,2 this study is the first to show that even slightly depressed levels of thyroid hormone may impair the ability to become pregnant.1
The researchers determined that low thyroid function was twice as common among women with unexplained infertility as it was among those without the condition. The study can be accessed online ahead of print in the Journal of Clinical Endocrinology & Metabolism.
Between 7% and 15.5% of women of reproductive age in the United States experience infertility, which is considered the inability to conceive a child after 12 months of sex without use of birth control, according to the Centers for Disease Control and Prevention.3 The source of the difficulty was identifiable for most of these women; for roughly 10%-30% the infertility is unexplained.3
The is well-documented. Laboratory data show that the hormone plays an important role in the proper development and implantation of eggs. Data also indicate that infertility affects nearly half of women with Hashimoto’s thyroiditis and Graves’ disease, both of which are marked by low thyroid function.
The American Thyroid Association recommends that physicians evaluating women for infertility assess TSH levels for severe abnormalities. However, no such guidance exists for infertile women with thyroid function that falls within the normal range.
For the new study, the researchers, led by Tahereh Orouji Jokar, MD, a neuroendocrinologist at Massachusetts General Hospital and Harvard Medical School, both in Boston, assessed levels of thyroid-stimulating hormone (TSH) in 187 women with unexplained infertility, as well as 52 with no evidence cause of infertility other than having a partner with absent or poor sperm. The women were treated at Mass General between 2000 and 2012.
The researchers used a cut-off of TSH levels of at least 2.5 mIU/L as their definition of subclinical hypothyroidism.That threshold is somewhat lower than the upper limit of normal for most TSH assays, which ranges between 4.5 and 5 mIU/L, according to the researchers. However, some experts believe the true normal range tops out at the lower level.
“The problem with lowering the cut-off to 2.5 though is that we will dramatically increase the number of people diagnosed with an underactive thyroid and we don’t have data demonstrating negative consequences of a TSH greater than 2.5,” said Pouneh K. Fazeli, MD, a neuroendocrinologist at Harvard Medical School, and senior author of the study.
“The goal of this study was to figure out if high-normal TSH levels do potentially negatively impact women who are trying to conceive,” said Dr. Fazeli.
Levels of TSH were significantly higher in women with unexplained infertility than in women whose partners had severe male factor infertility (1.95 mIU/L vs. 1.66 mIU/L),1 according to the researchers. This pattern held after accounting for age, body mass index (BMI) and smoking status, they noted. The researchers also assessed levels of prolactin, which is linked to fertility, but found no difference between the two groups of patients.
However, the researchers acknowledged that their findings do not establish causality, or necessitate a change in recommendations for clinicians.
“Based on these data, we can not recommend thyroid hormone replacement at all as this was a cross-sectional study which showed an association between unexplained infertility and higher TSH levels,” Dr. Fazeli said, “Before treatment with thyroid supplementation can be recommended, further studies will need to be done to see if treatment with thyroid hormone replacement improves pregnancy outcomes.”
The Harvard research team hopes to conduct such a study in the future to see if treatment with thyroid hormone improves time to conception in this patient population.
A Clinical Care Perspective
Tamara Wexler, MD, PhD, clinical assistant professor at New York University School of Medicine in New York City, told EndocrineWeb, “I feel it is reasonable to test TSH and free T4 levels in women who are pursuing fertility, though currently, normal range results are not typically treated before pregnancy.”
Dr. Wexler said that her perspective is in line with recommendations from the Endocrine Society4 while other organizations including the American Congress of Obstetricians and Gynecologists (ACOG)5 and the U.S. Preventive Services Task Force discourage universal screening even during pregnancy.
“ACOG, in fact, recently strengthened its recommendation not to test all pregnant women, citing a lack of consistent and clear evidence linking subclinical hypothyroidism to adverse outcomes,” she said.
Dr. Wexler remains interested in the question of whether mild elevations in prolactin influence fertility.
“This was not addressed in the study by Jokar et al, as only women with normal prolactin levels were included in the analysis. However, there is good reason to investigate a link between infertility and mild elevations in prolactin, as well as TSH levels,” said Dr. Wexler, “That said, management decisions—whether to treat—cannot be based on association alone, and no causal link has been established.”
- Jokar TO, Fourman LT, Lee H, Mentzinger K, Fazeli PK. Higher TSH levels within the normal range are associated with unexplained infertility. J Clin Endocrinol Metab. 2017 Ahead of print. Available at: www.ncbi.nlm.nih.gov/pubmed/29272395. Accessed December 20, 2017.
- Verma I, Sood R, Juneja S, Kaur S. Prevalence of hypothyroidism in infertile women and evaluation of response of treatment for hypothyroidism on infertility. Int J Appl Basic Med Res. 2012;2(1):17–19.
- Centers for Disease Control and Prevention. Infertility. Available at: https://www.cdc.gov/nchs/fastats/infertility.htm. Accessed December 30, 2017.
- Alexander EK, Pearce EN, Brent GA, et al. 2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum. Thyroid. 2017, 27(3):315-389.
- American College of Obstetrics and Gynecologists. Practice Bulletin No. 148: Thyroid disease in pregnancy 2015;125(4):996-1005.
- LeFevre ML. Screening for Thyroid Dysfunction: U.S. Preventive Services Task Force Recommendation Statement. Ann Intern Med. 2015;162(9):641-650.
Updated on: 01/11/18 Continue Reading: Managing Thyroid Disease During Pregnancy, New ATA Guidelines
Trying to get pregnant with Hashimoto’s and an underactive thyroid
How hypothyroidism affects fertility
The thyroid hormones impact all cells in the body and are necessary for virtually all the bodily functions.
Thyroid hormones affect both female and male reproductive health — the right balance of thyroid hormones and a healthy immune system will determine one’s success of getting pregnant.
Thyroid hormones and fertility
Thyroid hormones are important in all the phases of egg growth, sperm maturation, and survival of a fertilized egg (1–3).
T3 hormone helps thicken uterine lining (endometrium), which is a prerequisite for implantation of a fertilized egg. T3 helps the fertilized egg move down the fallopian tubes towards the uterus, where it will be implanted (1–4).
An underactive thyroid disrupts the metabolism of the hormone estrogen, and it leads to the increase in levels of testosterone, follicle stimulating hormone, and luteinizing hormone. This changes ovulation patterns in women and may result in irregular menstrual cycles (5).
7 in 10 people who are hypothyroid but not diagnosed have irregular menstrual cycles. When people get diagnosed and placed on levothyroxine therapy, menstrual cycles become regular for 5 in 10 people (6).
About 4 in 10 women struggling with getting pregnant have subclinical hypothyroidism (7).
For man, an underactive thyroid can reduce sperm motility and cause abnormal sperm morphology, lower down testosterone, and other sex hormones (8–10).
Hashimoto’s and fertility
Being diagnosed with Hashimoto’s and having high levels of TPO and TG antibodies doubles the risk of fertility problems (7, 11).
With not much research done on this topic, there are still a lot of unknowns — but a general observation from multiple studies is that high antibody levels will cause problems with conceiving.
Assisted reproduction and thyroid hormones and Hashimoto’s
During the course of assisted reproduction techniques (ART) — like in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) — women inject themselves with high doses of sex hormones in order to stimulate growth of eggs containing follicles in the ovaries.
This ovarian stimulation causes a rapid increase in estrogen levels, which increases the demand for T3 and T4 and puts a massive strain on the thyroid. If taking levothyroxine, the dosage should be increased to meet this sudden and big demand for thyroid hormones (12,13), and it is best to keep TSH levels below 2.5 mIU/L even before the start of the treatment (14).
What may help?
Collaborating with your health care practitioner in order to improve your chances of conceiving can include (15–20):
Checking your thyroid function and testing if you have Hashimoto’s before starting to try to get pregnant.
Getting on the appropriate medication dose and keeping your TSH below 2.5mIU/L.
Getting vitamin D levels in a good zone: 37.5–50.0 μg (1500–2000 iu)
Getting enough selenium: 200 mcg per day
Making lifestyle changes to lower TPO and TG antibodies: a diet that will reduce inflammation and exercise to increase serotonin levels.
Download the BOOST Thyroid app to manage your thyroid health.