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The TSH, T 4 , T 3 and prolactin responses to consecutive infusions of a potent and stabilized thyrotrophin releasing hormone analogue, RX77368, in man
Author(s) -
ECKLAND D. J. A.,
LIGHTMAN S. L.
Publication year - 1988
Publication title -
european journal of clinical investigation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.164
H-Index - 107
eISSN - 1365-2362
pISSN - 0014-2972
DOI - 10.1111/j.1365-2362.1988.tb01031.x
Subject(s) - endocrinology , medicine , prolactin , trh stimulation test , thyrotropin releasing hormone , stimulation , hormone , endocrine system , basal (medicine) , peripheral , domperidone , in vivo , dopamine , biology , insulin , microbiology and biotechnology
The endocrine manifestations of a stabilized thyrotrophin releasing hormone (TRH) analogue, RX77368, have been investigated in six male volunteers. Infusions were given on two occasions, with a 5‐day interval between infusions. On the second exposure to RX77368, there was a significant reduction in the TSH response, despite normal basal T 3 and T 4 levels, while the response of prolactin to RX77368 was unaltered. Domperidone administered during the infusion of RX77368 caused a further elevation of prolactin levels, whilst TSH levels were unchanged. This study shows the differential regulation of thyrotrophs and lactotrophs in response to stimulation by a TRH analogue, and shows, for the first time, down‐regulation of the TSH response in vivo , in the presence of normal peripheral thyroid hormone levels. The T 3 response to infusions of RX77368 was less than to a bolus injection of TRH, despite a greater TSH response to the analogue, suggesting impaired biological activity of TSH released in reponse to an infusion of the analogue.