<prompt> A major causal factor in some cases of hypogonadism is:Reduced secretion of gonadotropin-releasing hormone GnRHHypersecretion of pituitary LH and FSH as the result of increased GnRHExcess secretion of testicular activin by Sertoli cellsFailure of the hypothalamus to respond to testosterone  <response>: Ans. A. Reduced secretion of gonadotropin-releasing hormone GnRHReduced secretion of GnRH will result in extremely low levels of circulating LH and FSH, causing testicular atrophy, as in Kallmanns syndrome. Hypersecretion of LH and FSH, increased activin, and an increased number of FSH receptors all lead to hyperfunction of the testis, not hypofunction. A failure of the hypothalamus to respond to testosterone increases LH, leading to increased Leydig cell androgens and testicular hypertrophy 