False-positive reactions sometimes occur in radioim-munoassays for the determination of hormones. The problem of interpreting these assays is compounded in cases of apparent hypergonadotropinemia and hyperprolactinemia without a morphological basis (e.g., gonadal failure, galactorrhea, or a pituitary adenoma). The present authors have encountered this phenomenon in a relatively large number of patients over a period of 7 years. In the study presented here, they attempted to delineate the nature of the atypical hormone activity found in the serum of patients with pseudohypergonadotropinemia and pseudohyperprolactinemia. Twenty patients (14 females and six males, aged 13ndash;75 years) were investigated.When the blood samples of the patients were subjected to a detailed analysis by the measurement of the various dilutions of the serum in the assay system. it became apparent that the activities measured with the antisera against LH. FSH. beta;hCG, alpha;hCG, prolactin, and LSH were not identical to those of the authentic hormones in the double-antibody system. To determine whether the serum samples of the patients contained heterophilic antibodies that would interfere with the double-antibody radioimmunoassay, the samples were preincubated with various volumes of normal rabbit serum and normal horse serum. The amount of the second antibody was doubled. Pretreatment with low amounts of rabbit serum resulted in a reduction of the beta;hCG concentration in most of the cases. Similarly, pretreatment with normal horse serum lowered the concentration of beta;hCG in seven of nine cases. By contrast, pretreatment of serum samples from pregnant women with rabbit or horse serum resulted in only a 10 per cent variation of the beta;hCG concentration.When the radioimmunoassay for LH. prolactin. TSH. and beta;hCG was performed according to the double-antibody method, the concentration of the proteohormones constantly exceeded the upper limit of the normal range in all
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