Context Kisspeptin–neurokinin B (NKB)–dynorphin neurons are critical regulators of the hypothalamic–pituitary–gonadal axis. NKB and dynorphin are hypothesized to influence the frequency of GnRH pulses, whereas kisspeptin is hypothesized to be a generator of the GnRH pulse. How these neuropeptides interact remains unclear. Objective To probe the role of NKB in GnRH pulse generation and to determine the interactions between NKB, kisspeptin, and dynorphin in humans and mice with a complete absence of NKB. Design Case/control. Setting Academic medical center. Participants Members of a consanguineous family bearing biallelic loss-of-function mutations in the gene encoding NKB and NKB-deficient mice. Interventions Frequent blood sampling to characterize neuroendocrine profile and administration of kisspeptin, GnRH, and naloxone, a nonspecific opioid receptor antagonist used to block dynorphin. Main Outcome Measures LH pulse characteristics. Results Humans lacking NKB demonstrate slow LH pulse frequency, which can be increased by opioid antagonism. Mice lacking NKB also demonstrate impaired LH secretion, which can be augmented with an identical pharmacologic manipulation. Both mice and humans with NKB deficiency respond to exogenous kisspeptin. Conclusion The preservation of LH pulses in the absence of NKB and dynorphin signaling suggests that both peptides are dispensable for GnRH pulse generation and kisspeptin responsiveness. However, NKB and dynorphin appear to have opposing roles in the modulation of GnRH pulse frequency.

X-linked adrenal hypoplasia congenita (AHC) is a disorder associated with primary adrenal insufficiency and hypogonadotropic hypogonadism (HH). The gene responsible for X-linked AHC, DAX1, encodes a member of the nuclear hormone receptor superfamily. We studied an extended kindred with AHC and HH in which two males (the proband and his nephew) were affected with a nucleotide deletion (501delA). The proband's mother, sister, and niece were heterozygous for this frameshift mutation. At age 27 yr, after 7 yr of low dose hCG therapy, the proband underwent a testicular biopsy revealing rare spermatogonia and Leydig cell hyperplasia. Despite steadily progressive doses of hCG and Pergonal administered over a 3-yr period, the proband remained azoospermic. The proband's mother, sister (obligate carrier), and niece all had a history of delayed puberty, with menarche occurring at ages 17-18 yr. Baseline patterns of pulsatile gonadotropin secretion and gonadotropin responsiveness to exogenous pulsatile GnRH were examined in the affected males. LH, FSH, and free alpha-subunit were determined during 12.5-24 h of frequent blood sampling (every 10 min). Both patients then received pulsatile GnRH (25 ng/kg) sc every 2 h for 6-7 days. Gonadotropin responses to a single GnRH pulse iv were monitored daily to assess the pituitary responsiveness to exogenous GnRH. In the proband, FSH and LH levels demonstrated a subtle, but significant, response to GnRH over the week of pulsatile GnRH therapy. Free alpha-subunit levels demonstrated an erratic pattern of secretion at baseline and no significant response to pulsatile GnRH. We conclude that 1) affected males with AHC/HH may have an intrinsic defect in spermatogenesis that is not responsive to gonadotropin therapy; 2) female carriers of DAX1 mutations may express the phenotype of delayed puberty; and 3) although affected individuals display minimal responses to pulsatile GnRH, as observed in other AHC kindreds, subtle differences in gonadotropin patterns may nevertheless exist between affected individuals within a kindred.

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Although delayed puberty is relatively common and often familial, its molecular and pathophysiologic basis is poorly understood. In contrast, the molecular mechanisms underlying some forms of hypogonadotropic hypogonadism (HH) are clearer, following the description of mutations in the genes KAL, GNRHR, and PROP1. Mutations in another gene, DAX1 (AHC), cause X-linked adrenal hypoplasia congenita and HH. Affected boys usually present with primary adrenal failure in infancy or childhood and HH at the expected time of puberty.DAX1 mutations have also been reported to occur with a wider spectrum of clinical presentations. These cases include female carriers of DAX1 mutations with marked pubertal delay and a male with incomplete HH and mild adrenal insufficiency in adulthood. Given this emerging phenotypic spectrum of clinical presentation in men and women with DAX1 mutations, we hypothesized that DAX1 might be a candidate gene for mutation in patients with idiopathic sporadic or familial HH or constitutional delay of puberty. Direct sequencing of DAX1 was performed in 106 patients, including 85 (80 men and 5 women) with sporadic HH or constitutional delay of puberty and patients from 21 kindreds with familial forms of these disorders. No DAX1 mutations were found in these groups of patients, although silent single nucleotide polymorphisms were identified (T114C, G498A). This study suggests that mutations in DAX1 are unlikely to be a common cause of HH or pubertal delay in the absence of a concomitant history of adrenal insufficiency. (J Clin Endocrinol Metab 84: [4497][4498][4499][4500] 1999) T HE ASSOCIATION of DAX1 (AHC) gene mutations with X-linked adrenal hypoplasia congenita (AHC) and hypogonadotropic hypogonadism (HH) is well established (OMIM: 300200) (1, 2). More than 50 different mutations in the gene encoding DAX-1 have been reported in this condition (3-6). Affected boys typically present with primary adrenal insufficiency in infancy or childhood. HH usually becomes evident later in life with failure of pubertal development (7,8).DAX-1 is an orphan nuclear hormone receptor that is expressed in the adrenal gland, gonads, hypothalamus, and pituitary gonadotropes (9). The HH caused by DAX1 mutations seems to involve deficits at both hypothalamic and pituitary levels (10 -13). DAX-1 is also expressed in Sertoli cells (14), and male Ahch (Dax1) knockout mice have disordered spermatogenesis and infertility (15). DAX-1 has a crucial role, therefore, in the development and function of the reproductive axis at multiple levels. Different approaches to counseling and treatment are needed for patients with DAX1 mutations compared to those with hypothalamic forms of HH, such as Kallmann syndrome (3,16).Recently, DAX1 gene mutations have been found in several men and women who have less typical reproductive phenotypes. These cases include: 1) partial HH in a man who presented later in life with mild adrenal failure (13); 2) HH, but normal adrenal function, in a woman who is homozygous for a DAX1 mutation thro...