Cytoplasmic oestradiol receptors have been reported in breast tumour tissue but not in the uninvolved tissue from the same patients. Since gynaecomastic tissue is highly predisposed to neoplastic transformation, such receptors were looked for in this tissue from 13 phenotypic males of whom 6 had Klinefelter’s syndrome. High affinity saturable binding (K_d ∼ 10^-10 M) of ³H-oestradiol-170 was found in the breast tissue from 12 of these patients by gel elution and dextran-coated charcoal techniques. The concentration of binding sites were found to range from 16 to 359 fmol/mg cytosol protein.Previous studies by the present authors showing steroid aromatising capacity and the present finding of specific oestradiol receptors in a ‘high-risk tissue’ in the absence of any histologically detectable neoplasms might be relevant in elucidating the natural history of breast cancer in such individuals.

A method for the quantitative estimation of the gonadotropin inhibiting material (GIM) in human urine is standardised using the ovarian ascorbic acid depletion test, the results being expressed in terms of and HCG units. A dose-response relationship with GIM is established. The reliability of the assay is demonstrated. Unlike other methods of assay this method is able to express precisely the quantity of GIM present in the urine. Preliminary data on GIM values in normal subjects as well as patients with endocrine disorders are presented.

Gonadotrophin-inhibiting material (GIM) was able to inhibit the binding of ¹²⁵I-hCG to rat Leydig cells, suggesting that its inhibiting properties are due to its ability to compete for the hCG binding sites on Leydig cells. Binding of fluorescein isothiocyanate-tagged GIM to Leydig cells was also seen. The effect of GIM on hCG-induced adenylate cyclase activation and testosterone production was also studied. It was found that there was a dose-dependent inhibition of both these effects.

In vitro transformation of precursors to androgens and oestrogens was studied in breast tissues from 7 phenotypic males with gynaecomastia and 3 normal females. All the tissues studied showed formation of dihydrotestosterone and oestrogens, thus demonstrating the presence of 5α-reductase and aromatizing enzymes. The results on the values of urinary oestrogens before and after surgical removal of the breast tissue substantiate the biosynthetic potential of gynaecomastic tissue. The aetiological significance of these findings vis-à-vis gynaecomastia is discussed.

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