[Male pseudohermaphroditism caused by partial insensitivity to androgens. Clinical and biochemical heterogeneity].

Male pseudohermaphroditism due to partial androgen insensitivity (PAI) may be suspected clinically in case of incomplete masculinization of external genitalia in spite of age related plasma androgen levels. In 25 children or adolescents in whom PAI was suspected, the 5 alpha-reductase activity of external genitalia fibroblasts, the number of androgen receptor sites (Bmax) and the affinity of receptors for dihydrotestosterone (Kd) were studied. Clinical expression of PAI is highly polymorphic (Prader's type I to type IV), when most children (18/25) were considered as males. In a single patient the very low 5 alpha-reductase activity permitted the diagnosis of 5 alpha-reductase deficiency. The number of receptor sites (fmoles/mg DNA) varied from 0 to 730. Mean Bmax of patients (282 +/- 187 fmoles/mg DNA) was statistically lower than that of normal subjects (642 +/- 220 fmoles/mg DNA), p less than 0.05. The 5 cases in whom receptor concentrations were normal may be related to a qualitative abnormality of the androgen receptor or to a "post-receptor" defect. On the contrary no significant differences in Kd values were found. Correlation between sexual ambiguity and the number of measured receptors was not possible. These results emphasize the clinical and biochemical heterogeneity of PAI. Nevertheless, the decrease in number of androgen receptor sites remains the major data for the biochemical diagnosis of PAI. Study of post-receptor "markers" (3 alpha-reductase activity, aromatase, collagen) might allow better analysis of cases with PAI in whom androgen receptor concentrations are normal.