Hypothyroidism

Hypothyroidism is a very common physiologic disorder characterized by underproduction of thyroid hormone, due to either dysfunction of the thyroid gland (primary hypothyroidism) or loss of pituitary TSH secretion (secondary/central hypothyroidism).  The clinical manifestations are broad, potentially affecting nearly every organ system, but are largely nonspecific, and the diagnosis is rarely definitively established without appropriate diagnostic testing.  Treatment of hypothyroidism is generally straightforward, but the consequences of mismanagement can be significant.

The most common symptoms of hypothyroidism are highly nonspecific and include weight gain, fatigue, cold intolerance, myalgias, menstrual irregularities, and cognitive and affective symptoms ( Table 1).  Asymptomatic cases are common, and patients may present with only a vague sense of unwellness or malaise.  Clinical signs are only somewhat more specific and include hypertension (especially diastolic hypertension), bradycardia, goiter, hyperlipidemia, and hyponatremia.  Patients also may have changes in the clinical status of a previously well-controlled condition (eg, worsening glycemic control in diabetes mellitus, worsening depression).