Thyroid, an organ that influences your metabolism
by MedPlus Team, September 27, 2016
Thyroid is a butterfly shaped organ located near the throat in front of the neck region. It is a gland that produces chemicals called hormones that play a vital role in regulating body metabolism, blood pressure, heart rate etc, as part of the endocrine system. The two main hormones that thyroid produces are Thyroxine (aka T4) and Triiodothyronine (aka T3). Thyroid uses iodine as a substrate to produce these vital hormones. T4 is the primary hormone secreted by the gland, a small portion of which is converted to triiodothyronine (T3) once it is released into the blood and tissues. T3 is the more active hormone.
Other important determinants of the thyroid function are TSH or Thyroid Stimulating Hormone and the proteins (Thyroglobulin) which carry the hormones in the blood and convey it to the tissues that utilize it. Changes in both these substances has an effect on the thyroid function along with any other problems that are intrinsic to the thyroid gland itself.
TSH is a hormone released by the pituitary gland located near the hypothalamus in the brain. TSH stimulates the thyroid gland to release more T4 & T3. It has a feedback loop with the thyroid gland and the amount of TSH in blood is determined by a number of thyroid hormones in the blood. So if thyroxine levels increase, then TSH levels will be low and vice versa. TSH is one of the most sensitive and earliest markers to diagnose thyroid problems.
Since the thyroid hormones require proteins for transportation to the end organs, conditions that result in protein deficiency can affect the activity of the thyroid gland. So these conditions have to be checked for and ruled out in case of any suspected or confirmed thyroid abnormality.
Health problems related to the thyroid gland are a result of either the under activity or the over activity of the thyroid gland, conditions known as Hypothyroidism and Hyperthyroidism respectively.
Under active thyroid (Hypothyroidism)
Deficiency in thyroid hormone leads to a slowing down of metabolism and other vital functions in the body. Symptoms can include:
- Increased sensitivity to cold
- heavier menstrual flow
- brittle hair and nails
If left untreated, severe hypothyroidism can cause obesity, joint pain, heart disease, and infertility and in very severe cases to coma and death. Symptoms of severe hypothyroidism can include:
- puffiness of the face, hands, and feet
- slowed speech
- decreased taste and smell
- thin eyebrows
- thickened skin
Treatment of hypothyroidism would include identifying and correcting the underlying cause and replacing thyroxine (T4) with a synthetic thyroid hormone.
Over active thyroid (Hyperthyroidism)
High amounts of T4, T3, or both can cause an excessively high metabolic rate, a condition known as hypermetabolic state. Symptoms may include a rapid heart rate, elevated blood pressure, hand tremors, excessive sweating and a low tolerance for heat. Hyperthyroidism can cause more frequent bowel movements, weight loss, and, in women, irregular menstrual cycles.
Hyperthyroidism is often accompanied by a swelling of the thyroid gland itself, a condition called goiter, which can be either symmetrical or one-sided. In graves disease, which is a diffuse swelling of the thyroid gland due to an abnormality in the auto-immune system, the eyes may also appear quite prominent, a sign called exophthalmos.
Other symptoms of hyperthyroidism include:
- irregular heartbeat
- difficulty sleeping
- fine, brittle hair
- hair loss
- nausea and vomiting
- breast development in men
- increased appetite
- inability to concentrate
The following symptoms if present indicate severe hyperthyroidism and require immediate medical attention:
- shortness of breath
- loss of consciousness
- fast, irregular heart rate
Treatment of hyperthyroidism is specific to the underlying cause of the condition and may include Anti thyroid medications, such as methimazole, radioactive iodine or surgery.