Pulsatile thyrotropin release in patients with untreated pituitary disease

Pulsatile and nocturnal TSH secretion was investigated in 16 healthy controls (group A) and 19 patients with untreated pituitary disease [7 were euthyroid without suprasellar extension (group B), 6 were euthyroid with suprasellar extension (group C) of pituitary lesions, and 6 were hypothyroid with or without suprasellar extension (group D)]. Pulse analysis was performed using Desade and Cluster algorithms. No changes were observed among groups A-D in mean 24-h TSH pulse amplitude [values given as mean +/- SD; Desade, 0.4 +/- 0.2 vs. 0.7 +/- 0.4 vs. 0.6 +/- 0.4 vs. 0.5 +/- 0.2 mU/L (P = NS); Cluster, 0.4 +/- 0.2 vs. 0.7 +/- 0.4 vs. 0.5 +/- 0.3 vs. 0.4 +/- 0.2 mU/L (P = NS)] or in the mean 24-h TSH pulse frequency (approximately 10 pulses/24 h). The mean 24-h TSH concentration was highly correlated to the mean 24-h TSH pulse amplitude in controls (r = 0.93; P < 0.001) and patients (r = 0.63; P < 0.01), but not to the mean 24-h TSH pulse frequency. The nocturnal TSH surge was similar in controls and euthyroid patients without suprasellar extension (group A, 1.0 +/- 0.6; group B, 1.3 +/- 1.3 mU/L; P = NS), but was decreased in euthyroid patients with suprasellar extension (group C, 0.3 +/- 1.0 mU/L; P < 0.05) and hypothyroid patients (group D, 0.4 +/- 0.4 mU/L; P < 0.05). The decreased nocturnal TSH surge was associated with a loss of the usual nocturnal increase in TSH pulse amplitude, whereas the usual nocturnal increase in TSH pulse frequency was maintained. In conclusion, 1) mean 24-h TSH pulse amplitude and frequency are unchanged in untreated patients with pituitary disease; and 2) patients with central hypothyroidism as well as euthyroid patients with suprasellar extension of pituitary lesions had a decreased nocturnal TSH surge associated with a loss of the usual nocturnal increase in TSH amplitude, but not TSH pulse frequency.