Lack of correlation between cerebrospinal fluid thyrotropin-releasing hormone (TRH) and TRH-stimulated thyroid-stimulating hormone in patients with depression

Background: It has been proposed that elevated central thyrotropin-releasin g hormone (TRH) is associated with the blunted thyroid-stimulating hormone (TSH) response to TRH in patients with depression. Few studies have directl y evaluated this relationship between central nervous system and peripheral endocrine systems in the same patient population. Methods: 15 depressed patients (4 male, II female, 12 bipolar, and 3,unipol ar) during a double-blind, medication-free period of at least 2 weeks durat ion, underwent a baseline lumbar puncture followed by a TRH stimulation res t. Cerebrospinal fluid (CSF) TRH and serial serum TSH,free thyroxine, triio dothyronine, prolactin, and cortisol were measured. A blunted response to T RH was defined as a delta TSH less than 7 mu U/mL. Results: There was no significant difference in mean CSF TRH between "blunt ers" (2.82 +/- 1.36 pg/mL) and "nonblunters" (3.97 +/- 0.62 pg/mL, p = .40) . There was no evidence of an inverse relationship between CSF TRH and base line or delta TSH. There was no correlation between CSF TRH and the severit y of depression or any other endocrine measure. Conclusions: These darn are not consistent with the prediction of hypothala mic TRH hypersecretion and subsequent pituitary down-regulation in depressi on; however, CSF TRH may be from a nonparaventricular nucleus-hypothalamic source (i.e., limbic area, suprachiasmatic nucleus, brain stem-dorsal raphe ) and thus, not necessarily related to peripheral neuroendocrine indices. ( C) 1999 Society of Biological Psychiatry.