Hypothyroidism

Abstract

Hypothyroidism is the clinical picture that one sees when the thyroid is unable to produce enough thyroid hormones, triiodothyronine (T₃) and thyroxine (T₄), to keep blood levels normal and to satisfy the needs of peripheral tissues. Most patients have primary hypothyroidism, a result of disease in the thyroid that destroys its ability to produce adequate thyroid hormones. Hypothyroidism is occasionally secondary, caused by disease in the pituitary gland or hypothalamus resulting in inadequate production of thyroid-stimulating hormone (TSH). This chapter discusses primary hypothyroidism. The clinical presentation of hypothyroidism is variable, but often includes symptoms such as cold intolerance, fatigue, constipation, hair loss, dry skin, and other symptoms of a sluggish metabolism. As previously discussed, these symptoms are nonspecific and the diagnosis is often missed for months or even years. The clinical picture varies from mild symptoms early in the disease to very severe symptoms, such as confusion, lethargy, and even coma in the later stages. Physical findings may include goiter, slow speech and thinking, very dry skin, and slow relaxation of deep tendon reflexes (“hung up” reflexes). As the patient’s mentation slo more severe disease, the patient is often unaware of how bad things are. This is partially the result of the slow and insidious onset of this disease in many people. Also, the nonspecific nature of the symptoms leads the physician to consider other diagnoses, such as depression, before a thyroid etiology is considered.