Assessment of serum luteinizing hormone during ovarian stimulation with gonadotrophins

An immunoradiometric assay (IRMA), using monoclonal antibodies with high affinity for human luteinizing hormone (HLH), was evaluated for quantitative measurement of serum LH after human chorionic gonadotrophin (HCG) administration in patients undergoing stimulation of multiple follicular development. Compared to a radioimmunoassay (RIA) commonly used to monitor serum LH, LH IRMA was more effective by several orders of magnitude in discriminating between HLH and HCG and showed no cross-reactivity at HCG concentrations normally found in serum after hormone treatment. Assays of serum samples obtained from 10 patients receiving HCG as part of an HMG/HCG protocol to induce ovulation for IVF/GIFT also demonstrated that RIA values were greatly affected by exogenous HCG. It was estimated that 17-32% of serum HCG was measured as serum LH in RIA. In contrast, determinations of serum LH by IRMA was not biased by exogenous HCG. Data from IRMA indicated that eight of the 10 patients showed a significant rise in LH secretion, relative to mean baselines, at either 12 or 36 h after administration. In one patient the rise had already occurred before HCG administration. When an LH rise occurred, either before or after HCG injection, mean values were 2- to 9-fold higher than those of baseline levels. Assuming that LH rises greater than 12 mIU/ml may relate to an endogenous surge of 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.(ABSTRACT TRUNCATED AT 250 WORDS)