Pulsatile Secretion of Thyrotropin in Man*

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Abstract
To examine pulsatile TSH secretion, serum TSH wasdetermined every 10min for 24h in 6 normal subjects and every 15 min in 10 euthyroid patients with underlying thyroid disease. Serum T4T3an d PRL were simultaneously measured in the 10patients. Pulsatile TSH secretion was identified in all individuals. There wasa highly significant correlation between the mean24-h TSH concentration and pulse amplitude (P < 0.001). There was a highly significant inverse correlation between the mean 24-h TSH concentration and pulse frequency (P 4 (or) T3 but did correlate with serum PRL(P =0.03)in patients with thyroid disease. We conclude that 1) TSH pulsations can be identified in normal subjects and patients with thyroid disease; 2) elevations in serum TSH levels correlate with an increase in pulse amplitude and a decrease in pulse frqeuency; 3) the nocturnal rise in serum TSHis associated with increases in both pulse amplitude(and frequency; and 4) peripheral serum T4 or T3concentrations are not closely associated with pulsatile TSH secretion.