In this disorder, thyroid hormone levels in the blood are too low because of a problem in the pituitary gland, thyroid gland, or hypothalamus (a crucial brain structure that governs many body functions). Hypothyroidism is most common in women. In the United States, the incidence is rising significantly in people ages 40 to 50.

What Causes it?

Hypothyroidism in adults is caused by inadequate production of thyroid hormone. Usually, this stems from thyroid gland dysfunction resulting from surgery (thyroidectomy), radiation therapy (particularly with radioactive iodine), inflammation, or chronic autoimmune thyroiditis (also called Hashimoto’s disease). Hypothyroidism may also occur if the pituitary gland fails to produce thyroid-stimulating hormone or if the hypothalamus fails to produce thyrotropin-releasing hormone.

Other causes include congenital errors of thyroid hormone synthesis, iodine deficiency (usually dietary), or use of antithyroid medications such as propylthiouracil (PTU).

What are its Symptoms?

Early symptoms of hypothyroidism are typically vague and include fatigue, forgetfulness, sensitivity to cold, unexplained weight gain, and constipation. Eventually, the person may experience mentally instability; dry, flaky, inelastic skin; puffY face, hands, and feet; hoarseness; swelling around the eyes; drooping eyelids; dry, sparse hair; and thick, brittle nails.

Other common symptoms include appetite loss, a swollen abdomen, abnormally heavy or long menstrual periods, decreased sex drive, infertility, impaired coordination, tremors, and involuntary rhythmic movements of the eyes.

Myxedema Coma

In people with hypothyroidism, infection, exposure to cold, and use of sedatives may trigger myxedema coma. This life-threatening emergency compromises many body systems. Myxedema coma usually develops gradually, but it may arise suddenly if stress aggravates severe or prolonged hypothyroidism. Without prompt treatment, myxedema coma can lead to shock and death.

Symptoms of myxedema coma include stupor, abnormally slow and shallow breathing, low levels of sodium and sugar in the blood, low blood pressure, and a reduced body temperature.

How is it Diagnosed?

Radioimmunoassay, a highly sensitive lab test, confirms hypothyroidism by showing low levels of the thyroid hormones triiodothyronine and thyroxine. Other lab findings that support this diagnosis include an increased level of thyroid-stimulating hormone when hypothyroidism is due to thyroid insufficiency; a decreased thyroid­stimulating hormone level when hypothyroidism is due to hypothalamic or pituitary insufficiency; and elevated blood cholesterol and triglyceride levels.

How is it Treated?

The person with hypothyroidism receives gradual thyroid hormone replacement with Levoxine and, occasionally, Cytomel.

A person with myxedema coma receives treatment to support vital functions while restoring normal thyroid function. To support blood pressure and increase the pulse rate, Levoxine and hydrocortisone are given intravenously. To restore normal breathing, the person receives supplemental oxygen and respiratory support. Other supportive measures include fluid replacement and antibiotics for infection.

A disorder of water metabolism, diabetes insipidus results from a deficiency of a hormone called vasopressin or antidiuretic hormone. It’s characterized by excessive consumption of fluids and profuse urination. The disorder has no relationship to the much better-known form of diabetes called diabetes mellitus.

Diabetes insipidus may start in childhood or early adulthood and is more common in men than in women. If the person with diabetes insipidus doesn’t have complications, the prognosis is good, and he or she can usually lead a normal life.

What Causes it?

Diabetes insipidus usually results from damage to the pituitary gland. This damage may result from a brain tumor, neurosurgery, a skull fracture, or head injury. Another form of the disorder, called nephrogenic diabetes insipidus, originates with kidney problems.

What are its Symptoms?

Typically, the person abruptly begins to urinate profuse amounts: usually 4 to 16 quarts per day of diluted urine, but sometimes as much as 30 quarts per day. As a result, the person is extremely thirsty and drinks large quantities of water to compensate for the body’s fluid losses. This disorder may also result in nighttime urination and, in severe cases, extreme fatigue from inadequate rest due to frequent voiding and excessive thirst.

Other characteristic features of diabetes insipidus include symptoms of dehydration (poor tissue turgor, dry mucous membranes. constipation, muscle weakness, dizziness, and low blood pressure).

How is it Diagnosed?

To diagnose diabetes insipidus, the doctor will order a urinalysis to evaluate the physical characteristics of the person’s urine. In diabetes insipidus, the urine contains a high percentage of water.

Another test, called a water deprivation test, provides further information about the person’s condition. In this test, baseline vital signs and weight are taken, and urine and blood analyses are done. Then the person is deprived of fluids. Hourly measurements then record the total volume of urine output, body weight, and the physical characteristics of his or her urine. Throughout the test, blood pressure and pulse rate are carefully monitored. Also during the course of the test, the person receives an injection of vasopressin; the response to this injection helps to determine if diabetes insipidus results from a problem with the person’s pituitary gland or a problem with his or her kidney .

How is it Treated?

Until the cause is identified and eliminated, administration of various forms of vasopressin or of a vasopressin stimulant can control fluid balance and prevent dehydration:

• Pitressin is a liquid preparation that’s administered under the skin or in the muscle several times a day because it’s effective for only 2 to 6 hours. This form of the drug is used in acute disease and as a diagnostic agent.

• DDAVP can be given as a nasal spray or by an intravenous injection or injection under the skin. This drug is effective for 8 to 20 hours, depending on the dosage.