ABSTRACT
This chapter focuses on the failing thyroid gland and its relevance to psychiatric diagnosis and maximizing treatment response. It reviews some important points regarding the regulation of thyroid hormones, laboratory assessment of thyroid function, our data on the “hypothyroidism or depression” dilemma, and recommendations for the evaluation of hypothyroidism. The thyroid is an endocrine gland and part of a neuroendocrine system called the Hypothalamic-Pituitary-Thyroid. The clinical signs and symptoms of thyroid failure and the DSM III criteria for major depression share so many common items that patients are distinguished only by comprehensive thyroid testing. Lithium-like radioactive iodine acts to produce a decrease in circulating thyroid hormone and at times this can lead to clinical hypothyroidism. A provocative test of thyroid function at the pituitary level is the Thyrotropin Releasing Hormone (TRH) thyroid test. The hypothalamus secretes a tripeptide hormone called TRH into the portal hypopheseal circulation which transports TRH to the pituitary gland.
