Characteristics of an antiluteinizing hormone isoantibody produced during gonadotropin induction of ovulation.

Production of an antihuman LH antibody was suspected in a woman with isolated LH deficiency who received human pituitary gonadotropin (hPG) to induce ovulation and who developed secondary drug failure associated with very high "serum LH' values. Binding of [125I]LH to various dilutions of the patient's serum was demonstrated by precipitation with polyethylene glycol or sheep antihuman immunoglobulin G (anti-IgG) but not by precipitation with sheep antihuman immunoglobulin M (anti-IgM). Unlabeled LH competitively displaced [125I]LH from a 1:200 final dilution of the patient's serum, and indicated a single class of binding sites with a binding affinity of 1.5 X 1011 M-1 and a binding capacity of 84 ng LH/ml serum. The isoantibody was reactive against antigenic determinants in hPG, LH, and hCG but not against human FSH. Further examination showed binding to the beta, but not the alpha, subunit of two LH preparations and to beta hCG. It is concluded that repeated administration of hPG to this patient with isolated LH deficiency evoked IgG isoantibody formation against the beta subunit of LH.