LACK OF SEASONAL-VARIATION IN ABNORMAL TSH SECRETION IN PATIENTS WITHSEASONAL AFFECTIVE-DISORDER

The circadian variations in thyroid-stimulating hormone (TSH) secretio n, with particular attention to the nocturnal serum TSH surge and the TSH response to thyrotropin releasing hormone (TRH), were measured in seven patients with seasonal affective disorder (SAD) and in eight nor mal controls. Both patients with SAD and normal controls were tested i n fall/winter, when patients were suffering depressive symptoms, and i n spring/summer, when patients were euthymic. The TRH tests were perfo rmed in the morning. In all tests, the mean peak TSH response to TRH w as significantly lower in the patients with SAD than in the normal con trols. No significant differences were observed in either group betwee n spring/summer and fall/winter tests. At both periods, patients with SAD showed normal TSH levels in the morning, but did not experience a nocturnal TSH surge. In this group, morning and night TSH levels were similar. In contrast, normal controls showed significantly higher TSH levels at night than in the morning. Serum-free thyroid hormone levels were in the normal range in all subjects. Morning and night serum cor tisol levels and 24-hour urinary cortisol concentrations were similar in all subjects.