Hypothyroidism is estimated to be present in over one percent of the population and up to five percent over the age of 60. While hypothyroidism is easily diagnosable through laboratory testing, most lab panels do not include it as a routine test. Many carry this diagnosis with overt symptoms, but most are asymptomatic particularly when the disease is mild. When advanced, it may cause symptoms that may lead to a medical emergency.
The thyroid gland controls the metabolic rate in the body. When body metabolism slows, both mental and physical sluggishness can develop. Particularly in older individuals, hypothyroidism can be mistaken for just the “normal” process of aging. However, blood pressure, heart function and fluid regulation may be adversely affected, and prompt treatment is required to restore normal body function.
Mild hypothyroidism generally escapes detection on a physical exam without a screening panel that includes thyroxine and thyroid stimulating hormone measurements (T4 and TSH). Patient complaints include weight gain, tiredness, weakness, mild shortness of breath on exertion, joint pains, and even reported depression. Further questioning may reveal cold intolerance, joint pains, myalgias, and prolonged bleeding from menstruation. While an enlarged thyroid gland may be part of the picture, hypothyroidism can occur without this finding. As hypothyroidism progresses, findings of high blood pressure, cardiac failure and significantly delayed reflexes become part of the picture.
Hypothyroidism is much more often than not a primary disease of the thyroid gland itself. Those treated for the opposite problem (hyperthyroidism or an overactive thyroid) may slip into hypothyroidism as a consequence of the treatment itself. Autoimmune disease, particularly a condition known as Hashimoto’s thyroiditis, causes the gland to gradually fail and not produce the necessary thyroid hormone needed by the body. Iodine deficiency (particularly in parts of the world where iodine is not supplemented into foods like bread and salt) and cases due to pituitary failure (secondary hypothyroidism) are less common causes.
Thyroxine (T4) and triiodothyronine (T3) are the body’s main active thyroid hormones. These levels are decreased in hypothyroidism. Because sometimes body proteins and other metabolic states cause abnormal binding to proteins and may affect the measured values, the best value for diagnosing hypothyroidism is TSH, or thyroid stimulating hormone. Think of the process as a feedback loop. The pituitary gland in the brain is the thyroid-regulating center. When thyroid levels are low, a signal from the pituitary tells the gland to produce more thyroid hormone, and TSH rises. The hormone charged with this is TSH. An elevated TSH level is the signal that more hormone is needed or the body’s supply is less than adequate. This combined with low thyroid hormone measurements make the diagnosis. When the cause is secondary (the pituitary is failing), both thyroid hormone and TSH levels may be simultaneously low, but then other pituitary hormones are likely low and the diagnosis is made through those coincidentally low values.
Untreated hypothyroidism, particularly in the older population, can become quite serious. Myxedema coma, the most severe form of hypothyroidism, may cause severe body decompensation. Heart disease, lowered blood pressure, subnormal body temperature and decreased heart rate can become life compromising. Additionally, myxedema is difficult to treat and must be done under monitored conditions with extreme caution. Dementia may also occur, and this condition has to be differentiated from prolonged low thyroid levels. Hormone replacement may reverse these changes.
Treatment of most cases of hypothyroidism can be accomplished with simple thyroid hormone supplementation in the form of a daily oral medication. T4 (Synthroid) may be taken once a day with excellent results, and sometimes combinations of T4 and the more active thyroid metabolite T3 are used. Proper dosage is established by blood testing and monitoring of TSH and symptoms. As different people have a different thyroid set point, the dosage is not a uniform dose for each individual.
Most underwritable thyroid disease is not ratable, with preferred status available to most all who do not have accompanying disease and who take their medication regularly. Hypothyroidism becomes ratable with diseases such as uncontrolled hypertension or cardiac abnormalities. Again, well-monitored replacement therapy is a key to the best result.