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The thyroid is a small butterfly-shaped gland located below the Adam's apple in your neck.
Thyroid hormones are chemical substances made by the thyroid gland, which is located in the front of the neck. This gland uses iodine to make thyroid hormones, which are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions (metabolism), and are involved in the circadian rhythms that govern sleep, among other essential functions.
The two most important thyroid hormones are thyroxine (T4) and triiodothyronine (T3). Thyroid stimulating hormone (TSH), which is produced by the pituitary gland, acts to stimulate hormone production by the thyroid gland. The pituitary gland is stimulated to make TSH by the hypothalamus gland in the brain. Normally, when thyroid hormone levels in the body are high, they will "switch off" the production of TSH, which in turn stops the thyroid from making more T4 and T3.
The thyroid also makes the hormone calcitonin, which is involved in calcium metabolization and stimulating bone cells to add calcium to bone.
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Thyroid hormones are needed for normal development of the brain, especially during the first 3 years of life. Intellectual disability may occur if a baby's thyroid gland does not produce enough thyroid hormone (congenital hypothyroidism). Older children also need thyroid hormones to grow and develop normally, and adults need the hormones to regulate the way the body uses energy (metabolism).
Problems occur when the thyroid gland becomes either underactive (hypothyroidism) or overactive (hyperthyroidism). Thyroid problems are more common in women than men. Cancer may also develop in the thyroid gland.
Thyroid Diseases’ Symptoms
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HYPOTHYROIDISM
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Hypothyroidism results in low levels of T4 and T3 in the blood. Not having enough T4 and T3 in the blood causes your metabolism to slow down.
Common symptoms include:
* coarse and dry hair
* confusion or forgetfulness (often mistaken for dementia in seniors)
* constipation
* depression
* dry, scaly skin
* fatigue or a feeling of sluggishness
* hair loss
* increased menstrual flow (women)
* intolerance to cold temperatures
* irritability
* muscle cramps
* slower heart rate
* weakness
* weight gain
If hypothyroidism isn't treated, the symptoms will progress. Rarely, a severe form of hypothyroidism, called myxedema, can develop. Symptoms of myxedema include:
* low body temperature
* dulled mental processes
* congestive heart failure, a condition where the heart cannot pump enough blood to meet the body's needs
Myxedema coma occurs in people with severe hypothyroidism who are exposed to additional physical stresses such as infections, cold temperatures, trauma, or the use of sedatives. Symptoms include the loss of consciousness, seizures, and slowed breathing.
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HYPERTHYROIDISM
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Hyperthyroidism results in high levels of T4 and T3 circulating in the blood. These hormones speed up your metabolism. Some of the most common symptoms include:
* increased heart rate with abnormal rhythm or pounding (palpitations)
* high blood pressure
* increased body temperature (feeling unusually warm)
* increased sweating
* clamminess
* feeling agitated or nervous
* tremors in the hands
* feeling of restlessness even though the person is tired or weak
* increased appetite accompanied by weight loss
* interrupted sleep
* frequent bowel movements, sometimes with diarrhea
* puffiness around the eyes, increased tears, sensitivity to light, or an intense stare
* bone loss (osteoporosis)
* stopped menstrual cycles
Graves' disease, in addition to the common symptoms of hyperthyroidism, may cause a bulge in the neck (goiter) at the location of the enlarged thyroid gland. It also causes the eyes to bulge out, which may result in double vision. Sometimes, the skin over the shins becomes raised.
If hyperthyroidism is left untreated or is not treated properly, a life-threatening complication called thyroid storm (extreme overactivity of the thyroid gland) can occur. Symptoms include:
* confusion
* coma
* fever
* high blood pressure
* irregular heartbeat, which can be fatal
* jaundice associated with liver enlargement
* mood swings
* muscle loss
* restlessness
* shock
* weakness
Thyroid storm, considered a medical emergency, can also be triggered by trauma, infection, surgery, uncontrolled diabetes, pregnancy or labor, or taking too much thyroid medication.
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