Estrogen and progesterone receptors in the human thymus

Thymus tissue samples from 8 prepubertal children of both sexes were analyzed for estrogen and progesterone receptors. With the use of an enzyme immunoassay, estrogen receptors in both the cytosol and nuclear fraction were detected. The mean concentration (+/- SD) of receptors in the cytosol fraction was 2.1 +/- 0.9 and for the sum of receptors in both fractions 2.8 +/- 1.0 fmol/mg of protein. In addition low concentrations of progesterone receptors (mean value +/- SD = 0.9 +/- 0.3 fmol/mg of protein) were detected in all investigated samples. The presence of estrogen receptors in the nuclear fraction and of progesterone receptors suggests that the estrogen receptors may be active in mediating a physiological response and thus supports the view that the human thymus is a target organ for estrogens.