Selective suppression of FSH as a possible approach for fertility regulation

Inhibin can exist in multiple forms. The size heterogeneity of inhibin (low and high molecular weight) is likely to be due to the purification procedures employed. However, irrespective of their size, both inhibin preparations are capable of suppressing circulating FSH levels. Since inhibin is a native hormone, the toxic effects after therapeutic administration are expected to be minimal. Inhibin is able to suppress only 70%-80% of the FSH secretion. Inhibin and the steroid (estrogen or androgen) may be involved in the physiological regulation of FSH. To completely suppress circulating FSH, administration of either a combination of inhibin and a steroid or a potent synthetic analogue of inhibin may be necessary. Inhibin has a very short half life in the adult animal, which may be due to the involvement of other testicular factors. Identification and characterization of these factors may help in prolonging effectiveness of inhibin.