Plasma testosterone levels in C57BL/6J male mice: effects of age and disease.

Plasma testosterone (T) was measured by radioimmunoassay in both healthy and diseased, mature (8-11 months) and senescent (29-31 months) C57BL/6J male mice. Pathological lesions in diseased mice included reticulum cell sarcoma and enlarged mesenteric lymph nodes. In healthy mice neither plasma T nor testicular weight differed between age groups. Median levels and 95 percentiles of plasma T in ng/ml were 1.12 (0.19-12.18) in mature mice and 1.17 (0-7.31) in senescent mice. In diseased mice testicular weight and the range of values of plasma T were significantly reduced. The marked decreased in plasma T and testicular weight in diseased senescent mice illustrates the importance of distinguishing between disease-related changes and effects of aging, per se.