Major depressives often have abnormalities in the secretion patterns of their anterior pituitary hormones and target endocrine gland hormones. There are changes in both basal hormone secretion and the responses of these hormones to perturbation tests. Considerable work has been done attempting to develop a clinical application for some of these changes as biological state markers of endogenous depression. Prominent among the changes is an overactivity of the hypothalamo-pituitary-adrenocortical (HPA) axis. The dexamethasone suppression test (DST), as a reflection of HPA axis activity, has been the most thoroughly investigated "biological test" in psychiatry to date. Considerably fewer studies have addressed more fundamental issues of HPA axis regulation in depression, such as the relationship between pre-DST cortisol hypersecretion and DST outcome. The next most widely investigated endocrine axis in depression has been the hypothalamo-pituitary-thyroid (HPT) axis. Most studies have dealt with the TSH response to exogenously administered thyrotropin releasing hormone. While blunted TSH responses have been found in depressives compared with normal controls, the frequency of blunted responses in other types of psychiatric patients has made this test marginally useful for differential diagnosis. The reported changes in other hormone axes, for example the blunted growth hormone response to several challenges noted in depressed patients, have not been investigated sufficiently thoroughly to support their general clinical use at present.(ABSTRACT TRUNCATED AT 250 WORDS)