Despite the fact that a number of alterations of the hypothalamic-pituitary-gonadal hormone axis have been identified in patients with testicular cancer, little is known about the gonadotrophin secretion pattern in such patients who have greatly increased human chorionic gonadotrophin (hCG) serum concentrations. The aim of this study was to assess this issue in detail using a longitudinal study design and a panel of highly sensitive and specific immunoassays. Eleven patients with non-seminomatous (n=11), and one with seminomatous testicular cancer with pretreatment hCG serum concentrations exceeding 10(5) pg/ml (>1000 mIU/ml) were selected and followed for a mean of 166 days (mean of 14 serum samples/patient) after initial diagnosis. Serum concentrations of hCG, its free alpha- (hCGalpha) and beta- (hCGbeta) subunits, human follicle-stimulating hormone (hFSH) and human luteinizing hormone (hLH) were determined by highly sensitive and specific enzymometric immunoassays based on a panel of monoclonal antibodies (MCA) established in our laboratory. A potential FSH-like activity (FSA) of hCG in the respective sera was determined by radioreceptor assays (RRA) for LH/CG and FSH. Specificity of FSA at the level of the receptor was assessed by MCA-based immunoabsorption studies. At diagnosis, hCG (9.8x10(7)+/-4.84x10(7) pg/ml; range 1.1x10(5)-5x10(8) pg/ml) was greatly increased and serum hFSH was undetectable (<9 pg/ml) in 11 patients, and one patient had very low, albeit detectable (approximately 30 pg/ml) hFSH concentrations. hLH was below the limit of detection (<2 pg/ml) in five individuals. During successful chemotherapy, hCG rapidly declined to physiological concentrations and hFSH/hLH returned to normal or even reached supraphysiological values. There was a highly significant negative correlation between hCG and hFSH (P=0.0001) and, to a lesser extent, hLH (P=0.0265). The ability of serum hCG to block the binding of [125I]rFSH (rat FSH) to its receptor was found to be 0.01-0.1% compared with the FSH standard; this could be reversed by an anti-hCG MCA. Addition of a specific MCA against hFSH blocked 3 microg/ml of the hFSH standard, but had no effect on the FSA of serum hCG in the FSH RRA. As observed during pregnancy, secretion of gonadotrophin -- particularly that of FSH -- is substantially or completely suppressed in patients with testicular cancer when serum hCG concentrations exceed 10(5)-10(6) pg/ml (approximately 10(3)-10(4) mIU/ml). As determined by RRA, the intrinsic FSA of tumour-derived hCG is most probably responsible for the suppression of hFSH in this group of patients with testicular cancer.

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