Thyroid function: Hypothyroidism - What happens to the body?

Hormone replacement, Heart, General, Women's Health | July 21, 2014 | Author: The Super Pharmacist

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Thyroid function: Hypothyroidism - What happens to the body?

What happens to the body when Thyroid function declines?

Thyroid hormones are produced by a fleshy gland in the neck, just in front of the voice box/Adam's apple, called the thyroid gland. Virtually every cell in the body needs thyroid hormone to function. While it is not exactly a fuel for cells, like sugar or fat, thyroid hormone sets the metabolic speed for the cell. In hypothyroidism, where the circulating levels of thyroid hormone are too low, the metabolic activity of cells slows down. In fact, metabolism slows down over almost the entire body, which causes a number of physical signs and symptoms.

Common symptoms of hypothyroidism

People are affected differently by having too little thyroid hormone circulating through the body. The most classic symptoms that occur from hypothyroidism are:

  • Fatigue
  • The inability to tolerate cold temperatures
  • Weight gain
  • Constipation
  • Shortness of breath during even mild exercise.

All of these factors can be attributed to slow metabolism. Fatigue, weight gain, and shortness of breath during exertion are signs that the body is not using energy properly. Likewise, constipation reflects a slowing of the gastrointestinal tract. Hypothyroidism may cause muscle aches, joint aches, dry skin, a hoarse voice, and swelling in the hands and feet. Thyroid hormone is also important for nerve cell function. People with hypothyroidism may complain of experiencing abnormal sensations, such as “pins and needles” (i.e., paresthesias). Neurons (i.e., nerve cells) are very sensitive to the effects of thyroid hormone. Conversely, too little thyroid hormone can interfere with the neurons ability to function properly. In severe cases of hypothyroidism, people may experience altered mental status and cognitive dysfunction because low thyroid hormone levels can affect nerve cells in the brain.

Signs of hypothyroidism

Symptoms are abnormal things that a patient experiences while signs are abnormal things that a physician is looking for during a physical examination (physical findings). People with hypothyroidism may be able to detect some of the signs of hypothyroidism. One of the most disconcerting group of signs caused by too little thyroid hormone are those that affect the face. People with hypothyroidism (usually moderate or severe disease) have puffy faces with swelling around the eyes. The hair of the eyebrows thins, and hair on the head may be come coarse, brittle, thin, and may fall out. Speech problems may be due to tongue enlargement or from a general slowness in speech and movement which occurs because of hypothyroidism's effect on the brain. Severe hypothyroidism can cause a profound decrease in mental ability called myxedema coma. Physicians are able to detect several abnormalities in the heart from hypothyroidism. The heart rate may be abnormally slow, a condition called bradycardia. Despite a slow heart rate, blood pressure might be increased. Fluid may accumulate in the space between heart and the tough, fibrous sheath around the heart called the pericardial sac. Fluid may also accumulate in the lungs (pleural edema/effusion) and in the abdomen (ascites).

Congenital hypothyroidism (Cretinism)

Congenital hypothyroidism is a severe form of hypothyroidism that occurs in infants and children. It occurs in geographic regions that have little iodine in the soil and in populations that do not supplement their salt with iodine. Every thyroid hormone molecule contains iodine. When people are iodine-deficient, they cannot produce normal amounts of functional thyroid hormone. Thyroid hormone is particularly important in infants and children during development. If children do not maintain adequate levels of thyroid hormone, they can develop severe and long-lasting effects. Most notably, hypothyroidism in infants can cause mental retardation. Moreover, children will not grow properly and have short stature throughout life. Hypothyroidism also delays the onset of puberty and sexual maturation. The historic term for congenital hypothyroidism (now considered pejorative and no longer used) is cretinism.

What do thyroid blood tests mean?

hypothyroidismPhysicians measure certain substances in the blood to determine whether someone is hypothyroid, hyperthyroid (too much thyroid hormone), or euthyroid (normal). The two main substances are thyroid stimulating hormone (TSH) and free T4, which is the active form of thyroid hormone. The results of these tests provide a snapshot of the current level of thyroid hormone, and also suggest a possible cause.

While thyroid blood test results can be complex, we will focus on tests that are of concern to someone with hypothyroidism. Someone who has hypothyroidism will have low levels of free T4 and high levels of TSH. This is because the body is trying to generate more thyroid hormone by increasing the level of TSH that is produced (but it is failing to have the intended effect on thyroid hormone levels).

Occasionally, a person may have subclinical hypothyroidism, which means that their blood levels are abnormal but they may not display any signs or symptoms of hypothyroidism. In this case, TSH levels will be abnormally high but free T4 levels may be normal or slightly lower. Because of this, physicians usually follow TSH levels rather than thyroid hormone levels to get a more accurate picture of a person's hypothyroidism. In fact, once the diagnosis of hypothyroidism is made, physicians may simply track TSH levels without measuring thyroid hormone levels.

Most people with hypothyroidism are treated with artificial thyroid hormone. People who are treated for hypothyroidism will usually see their TSH and free T4 levels return to normal. If they happen to receive too much artificial thyroid hormone, free T4 levels may be abnormally high and TSH levels could be abnormally low. Hypothyroidism treatment is aimed at achieving normal levels of both of these blood markers.

Other blood tests that may be abnormal in hypothyroidism

Cholesterol metabolism may be slowed, which can lead to high blood cholesterol. Homocysteine levels can be abnormally increased as well. Over the long-term, these changes can increase the risk of heart disease and stroke. People with hypothyroidism may be anemic, that is, having too few red blood cells. They may also be at increased risk for abnormal blood clots in their veins.1 Serum creatinine may be increased in as many as 90% of people with hypothyroidism.2 Elevated creatinine levels indicate reduced kidney function. The amount of sodium in the blood may be abnormally low as well, a condition called hyponatremia. Severe hyponatremia can cause any number of effects, some of which mimic the signs and symptoms of hypothyroidism.

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REFERENCES:

  1. Squizzato A, Romualdi E, Buller HR, Gerdes VE. Clinical review: Thyroid dysfunction and effects on coagulation and fibrinolysis: a systematic review. J Clin Endocrinol Metab. Jul 2007;92(7):2415-2420.
  2. Kreisman SH, Hennessey JV. Consistent reversible elevations of serum creatinine levels in severe hypothyroidism. Arch Intern Med. Jan 11 1999;159(1):79-82.
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