Unaltered pulsatile and circadian TSH release in euthyroid patients with endemic goitre

To evaluate the pathophysiological role of TSH in goitrogenesis we investigated pulsatile TSH secretion in 11 patients with a non-toxic goitre and in 11 healthy controls. Thyroid volume was 40 +/- 10 ml in the goitre group and 15 +/- 4 ml in the controls as measured by ultrasound. Blood was sampled continuously via an indwelling venous catheter at 10-min intervals over 24 h. Neither the mean 24-h serum TSH levels (goitre 1.1 +/- 0.5 vs controls 0.9 +/- 0.4 mU/l) nor the nocturnal surge of TSH were significantly different between the two groups. The average of the TSH pulse frequency (goitre 10.8 +/- 3.7 vs controls 9.6 +/- 3.5 pulses/24-h) and of the TSH pulse amplitude (goitre 0.4 +/- 0.2 vs controls 0.3 +/- 0.1 mU TSH/l) as analysed by DESADE programme (detection of secretory activity by discrete deconvolution) did not differ in the two groups. Furthermore, there was no correlation between the volume of the thyroid gland and the dynamics of the TSH secretion. We conclude that our data do not suggest a relevant pathophysiological role of TSH secretion in the development of non-toxic goitre in man.