Serum gonadotropin levels in patients with germ-cell tumors of the testis: interrelations, possible cross-reactions and interpretation of beta-HCG level.
The concentration of FSH, LH, LTH, testosterone and beta-hCG was estimated in 177 serum samples from 86 patients with malignant germ-cell tumors of the testis. The objectives of the investigation were the following: the detection of interrelations of hypophyseal gonadotropins at different beta-hCG levels; the determination of the significance of borderline values of beta-hCG; the analysis of the effect of elevated concentrations of beta-hCG on pituitary gonadotropins: the detection of possible cross-reactions during gonadotropin determinations. The RIA method was used to estimate levels of three gonadotropins. The results revealed that there was no cross-reaction between FSH and beta-hCG at RIA assays. When the serum level of beta-hCG of tumor origin exceeded 100 U/l a subtotal inhibition of FSH secretion was observed. Pathologically increased values of beta-hCG were found not only in serum with subnormal-FSH levels, but also when FSH levels were excessively elevated (exceeding 50 U/l). In the latter case the elevated beta-hCG levels could possibly be the consequence of the secretion of beta subunits by the hypophysis or a cross-reaction with LH, and not of a tumor. With values of beta-hCG over 100 U/l cross-reaction with LH occurs, so the true LH levels cannot be assessed. For an adequate interpretation of elevated values of beta-hCG in the serum (i.e. whether they are tumor-derived or not), it is necessary to have values of FSH from the same serum sample.