Thyroid function, metabolic regulation, and depression.

Evidence suggests that alterations in thyroid function are associated with depression. Thyroid hormones also play an essential role in regulating metabolism. They influence the balance between metabolic rate and caloric intake and thus affect body weight changes. Appetite and weight disturbances are common in the syndrome of depression. There may be changes in resting metabolic rate in depression as well. Hence an interrelationship between thyroid function, metabolic regulation, and depression is suggested. A basic model of metabolic regulation is presented and linked to changes in mood and various indices of thyroid function. The model is offered as an initial framework for studying endocrine and metabolic components of depression. Testable hypotheses are generated through the use of the model, and research strategies are discussed.