Maximum nocturnal serum melatonin level (MTmax) in relation to some clinical variables was studied in 32 patients with a major depressive episode and in 33 healthy subjects with reference to the outcome of the dexamethasone suppression test (DST). Significant regressions were found between MTmax levels and clinical rating scores in CPRS, interpreted as retardation symptoms. Four healthy subjects with disposition for dysthymic reactions had subnormal MTmax levels, which differed from MTmax levels in subjects without such disposition. Patients but not the healthy subjects, who reported parental loss before 17 years of age, had subnormal MTmax levels and differed from patients with no reported parental loss. Patients with no reported suicidal behaviour in clinical history had significantly lower MTmax levels than patients with reported suicide attempts. No relations were found between low MTmax levels and diagnoses, duration of illness, reported inheritance for depressive illness or sleep disturbances. A hypothetical low melatonin syndrome in depression is proposed: low nocturnal melatonin, abnormal dexamethasone suppression test, disturbed 24-h rhythm of cortisol, less pronounced daily and annual cyclic variation in depressive symptomatology.

The baseline LH, FSH and testosterone levels and the LH and FSH response to TRH-LHRH administration (delta LH, delta FSH) were investigated in 28 patients meeting the RDC criteria for an acute major depressive disorder, and in 20 healthy persons. Twenty-two patients were also reinvestigated in a state of complete or partial clinical remission. Cross-sectional and longitudinal comparisons were made between the groups divided according to sex and menopausal status. After mathematical correction for age differences, the depressed males with an abnormal DST response showed significantly (P less than 0.03) higher delta FSH in the acute state compared to the controls. No relation could be established between the HPG axis hormone levels and the nocturnal serum melatonin levels or the PRL or TSH response to TRH-LHRH administration. In the longitudinal part of the study, the depressed males with an abnormal DST response showed decreased (P less than 0.03) testosterone levels and increased delta FSH (n.s.) in the acute state compared to remission, in contrast to the males with a normal DST. The present results do not support a hypothesis regarding a stimulus-induced down-regulation of the pituitary LHRH receptors in our patients. The possible mechanisms by which HPA axis activation (as revealed by an abnormal DST response) could influence the HPG axis in depressed patients remain to be elucidated.

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The serum levels of thyroxine and triiodothyronine (T4 and T3) were investigated at 10 different time points during a 24 h period in 31 inpatients meeting the RDC criteria for acute major depressive disorder. Twenty-three of these patients were also reinvestigated in a state of partial or complete remission. The results show that there was no significant difference in T4 or T3 levels during the 24 h period between depressed patients and 32 healthy controls despite significantly decreased TSH levels and TSH response to TRH administration (delta TSH) in the patient group. No indications were obtained that the patients' clinical presentation or depressive symptomatology as revealed by their CPRS scores, psychotropic medication, melatonin levels, or the outcome of the dexamethasone test, significantly influenced the T4 or T3 levels. The depressed patients who were studied longitudinally showed increased T4 levels in the acute phase compared to remission, whereas the T3 levels did not change. However, the levels of thyroid hormones were within the normal range in the acute phase as well as in remission. Furthermore, the changes in thyroid hormones between the state of relapse and remission were not significantly correlated to the corresponding increase in TSH levels and delta TSH between the two assessments. The present results are consistent with the hypothesis that the mechanism behind the impaired TSH response to TRH in acute major depressive disorder is a downregulation of the pituitary TRH receptors.