[Presence of high-affinity binding sites for thyroliberin in human pituitary adenomas secreting prolactin]

Specific high affinity binding sites for thyrotropin-releasing hormone (TRH) were demonstrated on cellular membranes from human prolactin-secreting adenomas in spite of the lack of in vivo prolactin response to TRH. One binding site was characterized. The mean value for the Kd from four adenomas was 64.8 +/- 12.5 nM. The maximal number of binding sites varied from one adenoma to another (from 80 to 450 fmoles/mg membrane proteins).