Evidence of sex difference in dopaminergic modulation of serum TSH secretion in primary hypothyroidism.

Abstract

We have demonstrated the sex difference with respect to the dopaminergic modulation of serum TSH secretion in patients with primary hypothyroidism. Ten patients, 4 men and 6 women, with hypothyroidism were given 10 mg of Domperidone (Domp) iv, a very potent and specific dopamine receptor blocking agent, which could not readily cross the blood brain barrier. There was a significant rise in the TSH level after Domp iv in female patients with primary hypothyroidism, from basal values at zero time at 74.4 +/- 33.8 (M +/- SE) microU/ml to 171.2 +/- 94.9 at 30 min (p less than 0.001), 159.6 +/- 100.5 at 60 min (p less than 0.001). In contrast, no significant change in serum TSH values after Domp iv occurred in male patients with primary hypothyroidism, from basal values at zero time of 181.1 +/- 39.9 microU/ml to 171.4 +/- 31.1 at 30 min, 180.7 +/- 33.2 at 60 min and 172.7 /+- 31.0 at 90 min. After thyroid hormone therapy, max delta TSH values and the change from basal to peak values were significantly related to basal TSH values in female patients with primary hypothyroidism (r = +0.93, p less than 0.001), while max delta TSH in male patients was inversely related to basal TSH values within the limited concentrations (r - =0.78, p less than 0.02). It was conjectured from our results that maximum TSH responses to intravenous administration of domperidone in male and female hypothyroid patients were observed in respectively different basal TSH values, that is, less than 100 microU/ml in males and more than 100 microU/ml in females. Our findings provided evidence of sex difference in dopaminergic modulation of TSH secretion in primary hypothyroidism.