I have long been trying to establish whether hcg does infact cause negative feedback and reduce lh secreation.
The below study suggests there is no such feedback and hcg infact boosts lh production. hmmm...... any thoughts
Endogenous luteinizing hormone surges following administration of human chorionic gonadotropin: further evidence for lack of loop feedback in humans.
Nader S, Berkowitz AS.
Department of Obstetrics, Gynecology and Reproductive Sciences, University of Texas Medical School, Houston 77030.
The existence of inhibitory short- and ultrashort-loop feedback mechanisms for luteinizing hormone (LH), while documented in animals, has been questioned in humans. Since human chorionic gonadotropin (hCG) binds to LH receptors but can be distinguished from LH in immunoassays, it is possible to identify LH surges in the face of exogenously administered hCG. The present study demonstrates LH surges at midcycle in normal volunteers and in women undergoing controlled ovarian hyperstimulation, given hCG. This provides further evidence for lack of loop feedback control of LH secretion in humans.
Inability to demonstrate an ultrashort loop feedback mechanism for luteinizing hormone in humans.
Kyle CV, Griffin J, Jarrett A, Odell WD.
Department of Internal Medicine, University of Utah School of Medicine, Salt Lake City 84132.
hCG has biological properties similar to those of LH, but can be measured separately from LH by current radioimmunometric assays. To investigate the possible existence of an autoregulatory mechanism for LH in humans, we compared the basal LH concentrations and the LH response to a GnRH stimulus with and without prior administration of hCG. On two separate occasions, at least 1 week apart, six normal (eugonadal) males and six normal postmenopausal females were given, in random order, either 10,000 IU hCG or saline followed by iv injection of a 200-micrograms bolus of GnRH. Blood samples were then taken 30, 60, 90, 120, 180, 240, and 300 min after GnRH. Serum concentrations of LH and hCG were measured at each time by two monoclonal antibody sandwich assays developed in our laboratory. After exogenous hCG, serum hCG concentrations rose rapidly to 200-500 IU/L (15,000-35,000 pg/mL) in both the men and women, remaining at this high level throughout the study. In the men, sex steroid concentrations did not change in response to the hCG during the 9 study hours. Compared to saline-treated controls, hCG had no significant effect in either men or postmenopausal women on the basal LH concentration or the response to a GnRH bolus, as determined by peak response and area under the LH/time curve between 0-300 min after GnRH. We conclude that an ultrashort loop feedback mechanism for LH on its own secretion does not exist in humans, as assessed by the present protocol.
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