Correlative Studies between the Presence of Thyrotropin-Releasing Hormone (TRH) Receptors and the In Vitro Stimulation of Growth-Hormone (GH) Secretion in Human GH-Secreting Adenomas

Summary

Specific receptors for TRH were characterized on cellular membranes of 6 out of 13 somatotrophic adenomas obtained from acromegalic patients. These receptors had the same dissociation constant (Kd: 62 ± 10 nM) as those found in human PRL-secreting adenomas, but their maximal number of binding sites (Bmax: 76 ± 24 fmol/mg of protein) was six fold smaller. A good correlation was found between the presence of TRH receptors and the in vitro TRH-induced stimulation of GH secretion. The increase in GH release varied from 25 to 200%. It was thus concluded that these receptors are functional. However, why only some of the human somatotrophic adenomas possess TRH receptors and respond to TRH in vitro needs further investigations.

Key-Words:

TRH Receptors - TRH Stimulated GH Secretion - GH-Secreting Adenomas