Deficiency of thyroid hormone causes a syndrome of decreased energy, weight gain, cold intolerance, dry skin, constipation, mood changes and decreased cognitive capability.

Other symptoms may include:

This constellation of symptoms is very uncomfortable and it is sometimes the symptom complex that drives pituitary patients to seek medical attention. Replacement therapy consists of levothyroxine, which is an oral tablet taken once daily on an empty stomach. A variety brands are available (i.e., Synthroid, Levoxyl, Levothroid, etc.). Blood levels of thyroid hormones are then periodically measured and the dose of levothyroxine is adjusted to maintain normal levels.