Unraveling a Subgroup of Men With Unexplained Male Infertility—Men With Normogonadotropic Nonobstructive Azoospermia

The missing FSH upregulation in NNOA might be due to a testicular malfunction, as both FSH and testosterone were normal and NNOA spermatogenesis differed only after meiosis. Two explanations are possible: NNOA represents a phenotype in which spermatogenesis fails-different from NOA-only at the postmeiotic level, leaving FSH regulation unaffected, or the same mechanism underlies both NNOA and NOA, but the groups are at different stages of progression of the same disorder.