• Leydig cells;
  • cryptorchidism;
  • Klinefelter's syndrome;
  • testis


Testicular specimens from normal men and men with cryptorchidism (CR) or Klinefelter's syndrome (KS) were taken, processed for light microscopy, and stained with the avidin–biotin peroxidase complex method for immunohistochemical detection of testosterone. The Leydig cells were classified by their morphology (normal, multivacuolated, and pleomorphic Leydig cells) and by their staining affinity for anti-testosterone antibodies (T, T+, and T++ cells), and the average numbers of each cell type for each group of testes were calculated. Normal testes showed morpholigically normal interstitial Leydig cells (96·0 ± 10 per cent) and multivacuolated Leydig cells (4·0 ± 1 per cent). Cryptorchid testes showed normal Leydig cells (85·8 ± 11 per cent) and multivacuolated Leydig cells (14·2 ± 2·3 per cent). Men with KS showed normal Leydig cells (78·9 ± 9·1 per cent), multivacuolated Leydig cells (9·2 ± 1·2 per cent), and pleomorphic Leydig cells (11·0 ± 1·8 per cent). The percentage of T++ cells was higher in normal testes (29·4 ± 2·1 per cent) than in CR (11·4 ± 2·2 per cent) and KS testes (6·3 ± 0·7 per cent). This suggests reduced functional Leydig cell activity in CR and KS. Multivacuolated Leydig cells showed weaker immunostaining than did normal Leyding cells in all the testicular groups. No immunostaining was shown by pleomorphic Leydig cells. Intratubular Leydig cells were only found in CR and KS. Immunostaining was weaker in intratubular Leydig cells than in interstitial Leydig cells. This suggests that intratubular location reduces functional activity of Leydig cells.