Assessment of serum luteinizing hormone during ovarian stimulation with gonadortrophins

An immunoradiometrte assay (IRMA), using monoclonal antibodieswith high affinity for human luteinizing hormone (HLH), wasevaluated for quantitative measurement of serum LH after humanchorionic gonadotrophin (HCG) administration in patients undergoingstimulation of multiple folh'cular development. Compared toa radioimmunoassay (RIA) commonly used to monitor serum LH,LH IRMA was more effective by several orders of magnitude indiscriminating between HLH and HCG and showed no crossreactivityat HCG concentrations normally found in serum after hormonetreatment. Assays of serum samples obtained from 10 patientsreceiving HCG as part of an HMG/HCG protocol to induce ovulationfor IVF/GIFT also demonstrated that RIA values were greatlyaffected by exogenous HCG. It was estimated that 17–32%of serum HCG was measured as serum LH in RIA. In contrast, determinationsof serum LH by IRMA was not biased by exogenous HCG. Data fromIRMA indicated that eight of the 10 patients showed a significantrise in LH secretion, relative to mean baselines, at either12 or 36 h after adminstration. In one patient the rise hadalready occurred before HCG administration. When an LH riseoccurred, either before or after HCG injection, mean valueswere 2to 9fold higher than those of baseline levels. Assumingthat LH rises > 12 mlU/ml may relate to an endogenous surgeof LH, none of the patients showed a surge prior to HCG administration.On the contrary, the occurrence of an ‘LH surge’after HCG was apparent in four patients. These data demonstratethe application of monoclonal antibodies incorporated in anIRMA to study the occurrence of endogenous LH surges duringstimulation of follicular development by gonadotrophins.