- Serum inhibin B in combination with serum follicle-stimulating hormone (FSH) is a more sensitive marker than serum FSH alone for impaired spermatogenesis in men, but cannot predict the presence of sperm in testicular tissue samples. von Eckardstein, S., Simoni, M., Bergmann, M., Weinbauer, G.F., Gassner, P., Schepers, A.G., Nieschlag, E. J. Clin. Endocrinol. Metab. (1999)