Leydig cell hypertrophy and hyperplasia in adult rats treated with an excess of human chorionic gonadotrophin (hCG).

A morphometric study was undertaken to determine to what extent the increase in LEYDIG cell activity is related to an increase in their number and/or size. An attempt was also made to consider the morphological characteristics of the cells in terms of their probable functional capacity. Following 8 h to 3 d of excess hCG treatment, LEYDIG cells nuclear volume exhibited an increase of 16 to 18% while no significant increase in cells number was observed. By 7 d of hCG treatment, the nuclear hypertrophy (42%) coexisted with hyperplasia (33%). After 14 d of stimulation, a 41% augment in cells number and 31% increase in nuclear volumes were found. Such morphometric parameters were correlated with plasma levels of testosterone. The results suggest that hypertrophy plays a more important role in the enhancement of LEYDIG cells secretory activity in the initial phase of hCG stimulation. A subsequent hyperplasia seems to become relatively more important in longer periods of treatment. Our findings support the statement that both hCG dose and time of treatment, and consequently the plasma level of testosterone, are important parameters to be considered when the functional activity of LEYDIG cells is been evaluated by morphometric techniques.