Hypogonadism Caused by a Single Amino Acid Substitution in the β Subunit of Luteinizing Hormone

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Abstract
INFERTILITY occurs in approximately 10 to 20 percent of couples and can be attributed to a reproductive disorder in the man or woman with equal frequency.1 , 2 Among men, specific causes of infertility can be identified in only a minority.1 In a previously identified kindred in which several men were infertile, the proband had not undergone spontaneous puberty and had low testosterone and elevated luteinizing hormone concentrations in serum, a pattern of hormone values indicative of primary hypogonadism.3 However, testosterone secretion in response to the administration of exogenous luteinizing hormone and human chorionic gonadotropin was normal. Thus, the proband appeared to secrete luteinizing hormone that was not active, a suggestion supported by the demonstration that the hormone was biologically inactive when tested in in vitro bioassays.4 The occurrence of infertility in three maternal uncles and a family history of consanguinity suggested that members of the family may have had an inherited defect in the structure of luteinizing hormone.