- The Effects of Hypothyroidism on the Body
- Endocrine system
- Circulatory and cardiovascular systems
- Nervous system
- Respiratory system
- Digestive system
- Reproductive system
- Other systems
- Hypothyroidism: Overview, Causes, and Symptoms
- Hypothyroidism (Underactive Thyroid)Part 1: Too Little Thyroid Hormone
- Causes of Hypothyroidism
- Symptoms of Hypothyroidism
- Potential Dangers of Having Hypothyroidism
- Questions to Ask Your Doctor
- General Information/Press Room
The Effects of Hypothyroidism on the Body
The thyroid is the butterfly-shaped gland in your neck. This gland produces hormones that regulate your body’s energy use, along with many other important functions. Hypothyroidism is when the thyroid is underactive. When thyroid hormone production drops, your body’s processes slow down and change. Hypothyroidism can affect many different systems in your body.
Hypothyroidism can affect your metabolism, mental functions, energy level, and bowel movements. Depending on how low your thyroid hormone production drops, your symptoms might be mild to severe.
Sometimes symptoms like fatigue, weakness, and constipation can be hard to tell apart from other conditions. To confirm that you have hypothyroidism, your doctor will need to do blood tests to check your thyroid hormone levels.
When you have hypothyroidism, your body makes too little of the thyroid hormones T3 and T4. These hormones control your metabolism. They affect the way your body uses energy. As a result, many of your body’s main functions change and can slow down.
Circulatory and cardiovascular systems
Hypothyroidism slows your heart rate and weakens your heartbeat, making your heart less efficient at pumping blood out to your body. This can make you short of breath when you exercise. By narrowing your arteries, this condition can also raise blood pressure.
Hypothyroidism can lead to high cholesterol. Together, high blood pressure and high cholesterol can increase your risk for heart disease.
Untreated hypothyroidism can change how the nerves carry information to and from your brain, spinal cord, and body. This can cause a condition called peripheral neuropathy. Its symptoms include numbness, tingling, pain, or burning in the affected parts of your body.
Too little thyroid hormone weakens the muscles you use to breathe and makes your lungs work less efficiently. As a result, you may feel short of breath or have trouble exercising.
Hypothyroidism also makes it more likely to develop sleep apnea, which are pauses in breathing that happen while you sleep.
Hypothyroidism slows the movement of food through your stomach and intestines. Slowed digestion can lead to symptoms like heartburn, constipation, and bloating.
Women with hypothyroidism may have irregular periods, heavy periods, or missed periods. They can have trouble getting pregnant or be more likely to have a miscarriage if they do get pregnant.
Because too little thyroid hormone slows your body’s metabolism, it can cause general symptoms like:
- weight gain
- cold intolerance
- swelling of hands and feet
A lack of thyroid hormone can leave your skin dry and pale. It can also affect how you control your body temperature, making you sweat less than usual. Your hair — including the hair on your scalp and along the outer edges of your eyebrows — can become thin. Your nails may look different and become brittle.
Hypothyroidism can affect every part of your body, from your brain to your skin. Yet the condition is different in everyone. Some people have mild symptoms while others have more severe symptoms. Taking medication your doctor prescribes is important so you can manage this condition and its symptoms and maintain a healthy lifestyle.
Hypothyroidism: Overview, Causes, and Symptoms
Hypothyroidism (Underactive Thyroid)
Part 1: Too Little Thyroid Hormone
Hypothyroidism is a condition in which the thyroid gland is not able to produce enough thyroid hormone. Since the main purpose of thyroid hormone is to “run the body’s metabolism,” it is understandable that people with this condition will have symptoms associated with a slow metabolism.
While the estimates vary, approximately 10 million Americans are likely to have this common medical condition. In fact, as many as 10% of women may have some degree of thyroid hormone deficiency.
Hypothyroidism is more common than you would believe, and millions of people are currently hypothyroid and don’t know it. For an overview of how thyroid hormone is produced and how its production is regulated, check out our thyroid hormone production page.
Causes of Hypothyroidism
There are two fairly common causes of hypothyroidism. The first is a result of previous (or currently ongoing) inflammation of the thyroid gland, which leaves a large percentage of the cells of the thyroid damaged (or dead) and incapable of producing sufficient hormone.
The most common cause of thyroid gland failure is called autoimmune thyroiditis (also called Hashimoto’s thyroiditis), a form of thyroid inflammation caused by the patient’s own immune system.
The second major cause is the broad category of “medical treatments.” The treatment of many thyroid conditions warrants surgical removal of a portion or all of the thyroid gland. If the total mass of thyroid producing cells left within the body is not enough to meet the needs of the body, the patient will develop hypothyroidism. Remember, this is often the goal of the surgery for thyroid cancer.
But at other times, the surgery will be to remove a worrisome nodule, leaving half of the thyroid in the neck undisturbed. Sometimes, this remaining thyroid lobe and isthmus will produce enough hormone to meet the demands of the body. For other patients, however, it may become apparent years later that the remaining thyroid just can’t quite keep up with demand.
Similarly, goiters and some other thyroid conditions can be treated with radioactive iodine therapy. The aim of the radioactive iodine therapy (for benign conditions) is to kill a portion of the thyroid to prevent goiters from growing larger or producing too much hormone (hyperthyroidism).
Occasionally, the result of radioactive iodine treatment will be that too many cells are damaged so the patient often becomes hypothyroid within a year or two. However, this is usually greatly preferred over the original problem.
Learn More about Hypothyroidism: Hypothyroidism Slideshow: Causes, Symptoms, and Treatments
There are several other rare causes of hypothyroidism, one of them being a completely “normal” thyroid gland that is not making enough hormone because of a problem in the pituitary gland. If the pituitary does not produce enough thyroid stimulating hormone (TSH) then the thyroid simply does not have the “signal” to make hormone. So it doesn’t.
Symptoms of Hypothyroidism
- Weight gain or increased difficulty losing weight
- Coarse, dry hair
- Dry, rough pale skin
- Hair loss
- Cold intolerance (you can’t tolerate cold temperatures like those around you)
- Muscle cramps and frequent muscle aches
- Memory loss
- Abnormal menstrual cycles
- Decreased libido
Each individual patient may have any number of these symptoms, and they will vary with the severity of the thyroid hormone deficiency and the length of time the body has been deprived of the proper amount of hormone.
You may have one of these symptoms as your main complaint, while another will not have that problem at all and will be suffering from an entirely different symptom. Most people will have a combination of these symptoms. Occasionally, some patients with hypothyroidism have no symptoms at all, or they are just so subtle that they go unnoticed.
If you have these symptoms, you need to discuss them with your doctor. Additionally, you may need to seek the skills of an endocrinologist. If you have already been diagnosed and treated for hypothyroidism and continue to have any or all of these symptoms, you need to discuss it with your physician.
Potential Dangers of Having Hypothyroidism
Because the body is expecting a certain amount of thyroid hormone, the pituitary will make additional thyroid stimulating hormone (TSH) as a way to prompt the thyroid to produce more hormone.
This extra work at signaling the thyroid gland to keep producing TSH may cause it to become enlarged, leading to he formation of a goiter (termed a “compensatory goiter”). Left untreated, the symptoms of hypothyroidism will usually progress. Rarely, complications can result in severe life-threatening depression, heart failure, or coma.
Hypothyroidism can often be diagnosed with a simple blood test: the thyroid hormone panel. In some persons, however, it’s not so simple and more detailed tests are needed. Most importantly, a good relationship with a good endocrinologist will almost surely be needed.
Hypothyroidism is completely treatable in many patients simply by taking a small pill once a day. However, this is a simplified statement, and it’s not always so easy. There are several types of thyroid hormone preparations and one type of medicine will not be the best therapy for all patients.
Many factors must be considered in establishing a personalized plan for the treatment of hypothyroidism and it is different for every patient.
Questions to Ask Your Doctor
- What is the cause of my underactive thyroid (hypothyroidism)?
- Do I have Hashimoto’s disease?
- What do the results of my blood test mean?
- How long will I need medicine for my hypothyroidism and what are the side effects?
- What TSH level will you use as a target for me?
- After I’m in the optimal range, how often do you suggest I come back for blood tests to make sure my dosage needs haven’t changed?
- Am I at risk for related health problems?
- How quickly can I expect relief from my hypothyroid symptoms?
- Are there any lifestyle changes I can make to relieve my symptoms?
Once you have the answers to these questions, your doctor will have a better understanding of your concerns and needs, and can take all the information into consideration in formulating a thyroid management plan in discussion with you.
Updated on: 07/10/19 Continue Reading Hypothyroidism: Overview, Causes, and Symptoms
CLINICAL THYROIDOLOGY FOR PATIENTS
A publication of the American Thyroid Association
Summaries for Patients from Clinical Thyroidology (July 2010)
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THYROID AND PREGNANCY
First Trimester TSH levels between 2.5 and 5.0 are associated with increased pregnancy loss
What is the study about?
Thyroid hormone is essential for a baby to develop normally during pregnancy. For at least the first half of pregnancy, the fetus gets thyroid hormone from the mother, so it is important that the mother has normal thyroid function during this time. In the non-pregnant woman, normal thyroid function is attributed to a TSH level in the normal range, usually 0.5 – 5 mIU/L. However, the definition of a normal TSH during pregnancy has been changing over time. In 2007, The Endocrine Society recommended that all women on thyroid hormone replacement therapy (levothyroxine) have TSH less than 2.5 mIU/L during the first trimester and less than 3 mIU/L throughout pregnancy. This study investigated the rate of preterm (early) delivery and pregnancy loss in women without hypothyroidism but with a TSH in the upper range of normal (TSH 2.5-5 mIU/L).
The full article title: Negro R et al, Increased Pregnancy Loss Rate in Thyroid Antibody Negative Women with TSH Levels between 2.5 and 5.0 in the First Trimester of Pregnancy. J. Clin. Endocrinol. Metab. 95 (9): 2010.
What was the aim of the study?
The aim of this study was to evaluate the rate of preterm delivery and pregnancy loss in women without hypothyroidism who had a TSH between 2.5-5.0 mIU/L compared to women with TSH less than 2.5 mIU/L.
Who was studied?
The women in this study are a subgroup of a larger prospective study of thyroid function and pregnancy. This study included 4123 women who were all negative for anti-thyroid antibodies (ie no evidence of intrinsic thyroid disease) and had a TSH less than or equal to 5.0 mIU/L. Hyperthyroid women were excluded. The women were divided into two groups for evaluation: Group A had TSH levels less than 2.5mIU/L and Group B had TSH levels 2.5-5.0 mIU/L.
How was the study done?
All pregnant women in the study had a FT4 and TSH drawn during the first trimester. They were then followed normally throughout pregnancy. Pregnancy outcomes were recorded and the rates of pregnancy loss and preterm delivery were compared between women in the two groups.
What were the results of the study?
A total of 3481 (84.4%) pregnant women had a TSH less than 2.5mIU/L during the first trimester and were in Group A. The remaining 642 women (15.6%) were in Group B and had a first trimester TSH between 2.5-5.0m IU/L. The average TSH of the women in Group A was 0.82 compared to an average TSH of 3.14 in the women in Group B. The spontaneous pregnancy loss rate was significantly lower in the women in Group A compared to Group B. Only 3.6% of women with a TSH less than 2.5 during the first trimester (Group A) had a spontaneous pregnancy loss versus 6.1% of the Group B women with a TSH 2.5-5.0 mIU/L. There were no significant differences in rates of preterm delivery.
How does this compare with other studies?
Several studies have suggested that hypothyroidism is associated with pregnancy loss but the results in women with subclinical or mild hypothyroidism have been somewhat conflicting. Studies of women during pregnancy have suggested the TSH normal range is not the same as for non-pregnant individuals but the exact range had not been clearly identified. This study is the first to examine pregnancy loss and preterm delivery in women with TSH in the 2.5-5.0mIU/L range, which is generally considered to be the upper half of the normal range in non-pregnant individuals.
What are the implications of this study?
The clinical implication of this study is that a TSH greater than 2.5 mIU/L may not be normal during the first trimester of pregnancy. This study suggests that the upper limit of the TSH normal range should be redefined as less than 2.5 mIU/L during pregnancy.
— Whitney Woodmansee, MD
ATA THYROID BROCHURE LINKS
Thyroid and Pregnancy: http://www.thyroid.org/patients/patient_brochures/pregnancy.html
Thyroid Function Tests: http://www.thyroid.org/patients/patient_brochures/function_tests.html
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General Information/Press Room
Prevalence and Impact of Thyroid Disease
More than 12 percent of the U.S. population will develop a thyroid condition during their lifetime.
- An estimated 20 million Americans have some form of thyroid disease.
- Up to 60 percent of those with thyroid disease are unaware of their condition.
- Women are five to eight times more likely than men to have thyroid problems.
- One woman in eight will develop a thyroid disorder during her lifetime.
- Most thyroid cancers respond to treatment, although a small percentage can be very aggressive.
- The causes of thyroid problems are largely unknown.
- Undiagnosed thyroid disease may put patients at risk for certain serious conditions, such as cardiovascular diseases, osteoporosis and infertility.
- Pregnant women with undiagnosed or inadequately treated hypothyroidism have an increased risk of miscarriage, preterm delivery, and severe developmental problems in their children.
- Most thyroid diseases are life-long conditions that can be managed with medical attention.
Facts about the Thyroid Gland and Thyroid Disease
The thyroid is a hormone-producing gland that regulates the body’s metabolism—the rate at which the body produces energy from nutrients and oxygen—and affects critical body functions, such as energy level and heart rate.
- The thyroid gland is located in the middle of the lower neck.
- Although the thyroid gland is relatively small, it produces a hormone that influences every cell, tissue and organ in the body.
- Hypothyroidism is a condition where the thyroid gland does not produce enough thyroid hormone. Symptoms include extreme fatigue, depression, forgetfulness, and some weight gain.
- Hyperthyroidism, another form of thyroid disease, is a condition causing the gland to produce too much thyroid hormone. Symptoms include irritability, nervousness, muscle weakness, unexplained weight loss, sleep disturbances, vision problems and eye irritation.
- Graves’ disease is a type of hyperthyroidism; it is an autoimmune disorder that is genetic and estimated to affect one percent of the population.
Research Advancements in Thyroid Disease
Research funded by the American Thyroid Association over the past 40 years has accomplished:
- Mandatory screening of newborns for congenital hypothyroidism, and early treatment that has prevented mental retardation.
- Cost-effective methods to detect thyroid cancer by screening the 250,000 thyroid nodules developed in Americans each year.
- Groundbreaking work in brain development and thyroid hormone function.
- Promising Graves’ disease genetic research that may lead to improved prognosis and new preventive treatments.
- An experimental drug that may prove useful for treatment and prevention of eye problems associated with Graves’ disease.
89th Annual Meeting of the American Thyroid Association
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