The effect of GHRH on TSH release in rats in vivo and in vitro.

Journal of endocrinological investigation1995PMID: 7615907

Animal StudyIn VitroSermorelin

Plain Language Summary

In rats, GHRH was shown to boost the thyroid-stimulating hormone (TSH) response to TRH specifically in the evening, but not in the morning or in isolated pituitary cells. This time-dependent effect suggests GHRH enhances TSH release through an indirect brain mechanism, possibly by reducing somatostatin inhibition during evening hours.

Abstract

In man, GHRH has been shown to potentiate the TSH-releasing activity of TRH. To study the way by which GHRH affects TRH-stimulated TSH release, we examined the effect of GHRH (1-29)NH2 on basal and stimulated TSH secretion in intact male rats and superfused dispersed rat pituitary cells. In the intact rats, GHRH(1-29)NH2 potentiated TRH-stimulated TSH release in the evening, but potentiation was not observed in the morning and in dispersed pituitary cells. Basal TSH levels were not changed by GHRH(1-29)NH2. It is concluded that GHRH(1-29)NH2 potentiates the TSH-releasing activity of TRH in the evening in rats possibly through suprahypophyseal disinhibition.

Authors

Looij, B J; Nieuwenhuijzen Kruseman, A C; Roelfsema, F; van der Heide, D; Hoogma, R P; Schröder-van der Elst, J P