August 18, 2011

The Thyroid Gland: Little Organ, Big Action

The thyroid gland is one of the most active hormone-producing glands in the body. It is located on the frontside of the neck, just above the collarbone and below one’s Adam’s apple. It is butterfly-shaped with the wings wrapping around the protective shielding of the larynx.
It is a little organ but highly active. The thyroid gland controls metabolism, the ability of the rest of the body to use energy. It also regulates how responsive the body should be to other hormones regulating growth. Importantly, its function has a direct effect on the ability to become pregnant and to maintain a healthy pregnancy.
The ability to control the body’s metabolism is governed by the thyroid hormones produced in the gland. The major hormones produce are triiodothryonine (T3) and thyroxine (T4). They are named according to how many Iodine molecules are attached to the hormone structure; for instance, thyroxine has 4 iodine molecules attached. Within the thyroid gland, one Iodine molecule is removed from thyroxine generating T3. The balance between T3 and T4 strictly controls the body’s metabolism. The control for how much T3 and T4 are made within the thyroid gland is governed by the pituitary gland of the brain. It makes a hormone called TSH (thyroid stimulating hormone) which is essentially a volume control for the thyroid gland function. If metabolism is slower, the brain makes more TSH in hope that the thyroid will generate more thyroid hormones. If the thyroid gland is making too much T3 and T4, the brain will lower the dial of TSH production and the TSH levels will decrease; similar to lowering the volume of the radio if it is too loud.
Variations in thyroid function are normal. The most common problems related to thyroid function are an overactive thyroid – hyperthyroidism and an underfunctioning thyroid – hypothyroidism. They each present with very different symptoms. Hyperthyroidism can present with rapid weight loss, excessive hunger, anxiety, menstrual irregularities, heart palpitations and later presentation of prominent (almost bulging) eyes. While hypothyroidism is associated most often with weight gain, fatigue, depressive symptoms and constipation. Both thyroid gland abnormalities can affect reproduction. Assessing thyroid function is a component of a general physical as well as essential in the workup of couple who have concerns with fertility.

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Danielle Vitiello, Ph.D., M.D.

Danielle Vitiello, Ph.D., M.D. Board-Certified in Obstetrics and Gynecology, Reproductive Endocrinology and Infertility