By Rachel Pessah-Pollack, MD

“Doctor, I’m gaining weight.  Is my thyroid not working?”

One of the most common reasons why a patient will see an endocrinologist (physicians who specialize in hormone problems) is a concern that their weight gain may be due to a problem with their thyroid gland. While most of the time weight gain is a function of too many calories and not enough exercise, it is important to understand how the thyroid functions and what symptoms you may develop without enough thyroid hormone.

What is hypothyroidism?

Hypothyroidism is a condition in which the thyroid gland does not produce enough thyroid hormone. The thyroid gland is located in the center of the neck and regulates the body’s metabolism.  Production of thyroid hormone (T3 and T4) is regulated by your pituitary gland, which is located in your brain.  The pituitary gland produces thyroid-stimulating hormone (TSH), giving a signal to the thyroid gland to produce more thyroid hormone (T3 and T4).  When the thyroid is under-active, the pituitary gland makes more TSH in order to stimulate the thyroid gland to make more T3 and T4. Therefore, hypothyroidism is associated with a high TSH and low T3 and T4.

How can I tell if my thyroid is under active?

The diagnosis is usually made by a blood test measuring the TSH level.  Some people with hypothyroidism have a swollen neck due to a goiter (enlarged thyroid gland), but not all patients have this. The symptoms that may be seen with an under-active thyroid may overlap with symptoms of many other diseases.  These symptoms include:

  1. Fatigue.
  2. Weight gain.
  3. Constipation.
  4. Menstrual changes.
  5. Difficulty concentrating.
  6. Dry skin and brittle fingernails.
  7. Hair loss.
  8. Feeling cold.
  9. Loss of memory.

It is important to recognize that having these symptoms does not necessarily mean your thyroid is under-active.  Testing your blood’s TSH level can help determine if your thyroid is functioning appropriately. The more severe the hypothyroidism, the higher the TSH level and the lower the T4 level will be. If you suspect you may have hypothyroidism, seeing your primary care physician or endocrinologist should be your first step. If your levels are borderline and you do not have any symptoms or underlying medical reason requiring treatment (for example, planning a pregnancy), you may not need medication and can be followed closely. If your TSH level is mildly elevated and you are having symptoms (such as those mentioned above), your doctor may suggest a trial of medication to see if your symptoms improve.

Why is my thyroid under-active?

There are many causes of hypothyroidism.

  1. Hashimoto’s thyroiditis (also called chronic autoimmune thyroiditis) is the most common cause of thyroid failure. Autoimmune thyroid disease has been estimated to be as high as 5 to 10 times more common in women than in men. This condition is due to an “autoimmune” process in which your body makes antibodies that gradually disable the thyroid gland. This type of hypothyroidism tends to run in families.
  2. Surgical removal of the thyroid gland.
  3. Radiation treatment or exposure.
  4. Certain medications.
  5. Viral illnesses that can attack the thyroid gland.
  6. Hypothyroidism present at birth.

How is an under-active thyroid treated?

As the thyroid gland becomes unable to produce enough thyroid hormone, treatment with a thyroid hormone supplement becomes necessary. The most common form of thyroid replacement is with levothyroxine, which works in the same way your own thyroid hormone would work. Levothyroxine is best taken on an empty stomach in the morning, one hour before breakfast and four hours before taking other medications including vitamins.  If levothyroxine is taken with other medications or vitamins (for example oral calcium or iron), the amount absorbed is lower and you may need a higher dose of medication to achieve normal thyroid levels. Your physician will adjust your dose depending on how you take your medication.

Some people find their symptoms improve within a few weeks of starting thyroid hormone replacement. However, it can take longer than 3 months for others to start to feel better. Your doctor may repeat your TSH level every 4 to 8 weeks until your levels have stabilized. The normal reference range can vary based on your age as well as if you are pregnant.  Pregnant woman with an under-active thyroid should be followed more frequently to ensure her TSH level stays in the normal range.

Who should be screened for hypothyroidism?

The American Thyroid Association (ATA) recommends that all adults be screened for thyroid problems with a TSH blood test beginning at age 35 and every five years thereafter. Nonetheless, there is no consensus regarding who should be screened for thyroid disease. Certain diseases increase the likelihood of developing thyroid problems and your TSH level should be checked if you have/are:

An autoimmune disease, such as type 1 diabetes or celiac disease.

  1. A first-degree relative (mother or father or sibling) with autoimmune thyroid disease.
  2. A history of high-exposure radiation to your head or neck (including treatment with radioactive iodine therapy for an overactive thyroid and external beam radiotherapy for head and neck cancer).
  3. A history of thyroid surgery or thyroid problems in the past.
  4. An abnormal thyroid exam.
  5. On medications that can affect your thyroid function (such as amiodarone or lithium).
  6. Pregnant.

Hypothyroidism is a very common and important condition.  While making the diagnosis solely based on symptoms can be challenging, an under-active thyroid can be easily diagnosed with a blood test. Once an under-active thyroid is diagnosed, treatment is effective and safe, allowing you to continue on the path to a healthy life.

Rachel Pessah-Pollack, M.D. graduated from SUNY Update Medical University in Syracuse in May, 2005. She completed her Endocrinology fellowship at Mount Sinai Medical Center, after which ProHEALTH was pleased to welcome her to our Division of Endocrinology. She is Board certified Internal Medicine and has a second Board certification with the American Board of Physician Nutrition Specialists. Her Board certification in Endocrinology is pending. Dr. Pessah-Pollack has a special interest in pregnancy-related endocrine disorders and has written numerous articles on the subject. She is currently editing a book on endocrine disorders during pregnancy and is co-authoring the American Association of Clinical Endocrinology’s “Diabetes During Pregnancy” Clinical Practice Guidelines.