Hormonal cut-offs of partial androgen deficiency: a survey of androgen assays.

While the typical symptomatology of severe hypogonadism in young adults permits the clinical diagnosis of hypoandrogenism, the diagnosis of partial androgen deficiency of the aging male (PADAM), as occurs relatively frequently in elderly males, is much more difficult. This is due to its clinical picture being subtle and aspecific, and to the fact that both clinical and biochemical evidence of androgen deficiency are required for the diagnosis. In the absence of a practical, clinical useful parameter of androgen activity, we have to rely upon bio-active plasma testosterone levels. Although the requirements of androgens in elderly males may be different from those in young, healthy adults, the lower limit of levels observed in the latter is generally used to define biochemical hypoandrogenism. Based on these data, we consider 11 nmol/l of testosterone, 0.225 nmol/l of free testosterone (FT) and 5.3 nmol/l of biotestosterone (bio-T) as the lower normal limits. As even when using the same kits, values for plasma testosterone and SHBG may differ significantly between laboratories, each laboratory should define its own normal values. As to the methodology, neither direct measurement of free testosterone by analog assay, nor the FT index (T/ SHB) can be recommended, only values obtained by dialysis, ammoniumsulfate precipitation or calculation yielding reliable estimates of androgen bio-activity. Dialysis and ammoniumsulfate precipitation are however work intensive and not widely used.