THYROID-FUNCTION TESTING IN PSYCHIATRIC-ILLNESS - USEFULNESS AND LIMITATIONS

The assessment of thyroid function in psychiatric patients may be obsc ured by several effects of the psychiatric condition on both thyroid h ormone and TSH levels. Acute psychiatric decompensation may result in elevation in total T-4 and free T-4 index, and less frequently in hypo thyroxinemia In addition, psychiatric illnesses can cause suppressed T SH levels, blunted TSH response to thyrotropin-releasing hormone (TRH) (particularly in depression), and elevated TSH values that may result in diagnostic errors. Ever though mechanisms similar to the ones resp onsible for thyroid function rest changes in other nonthyroidal illnes s could account for some of these abnormalities, other mechanisms invo lving dysregulation of hypothalamic-pituitary function seem to play an important role. TRH stimulation testing has also been used for the di agnosis and prognosis of some psychiatric disorders. This zest, howeve r; appears to have low sensitivity and specificity and little clinical usefulness far this purpose and may be replaced by basal TSH levels d etermined red by highly sensitive assays. In this review, in addition to discussing the usefulness and limitations of thyroid function tests in the setting of a psychiatric condition, we provide a stepwise appr oach, using sensitive TSH as a first-line test in the assessment of th yroid function in psychiatric patients. (C) 1997, Elsevier Science Inc .