Leptin and melanocortin signaling control ingestive behavior, energy balance, and substrate utilization, but only leptin signaling defects cause hypothalamic hypogonadism and infertility. Although GnRH neurons do not express leptin receptors, leptin influences GnRH neuron activity via regulation of immediate downstream mediators including the neuropeptides neuropeptide Y and the melanocortin agonist and antagonist, α-MSH, agouti-related peptide, respectively. Here we show that modulation of melanocortin signaling in female db/db mice through ablation of agouti-related peptide, or heterozygosity of melanocortin 4 receptor, restores the timing of pubertal onset, fertility, and lactation. Additionally, melanocortin 4 receptor activation increases action potential firing and induces c-Fos expression in GnRH neurons, providing further evidence that melanocortin signaling influences GnRH neuron activity. These studies thus establish melanocortin signaling as an important component in the leptin-mediated regulation of GnRH neuron activity, initiation of puberty and fertility.

Deficient leptin signaling causes infertility via reduced activity of GnRH neurons, causing a hypogonadal state in both rodents and humans. Because GnRH neurons do not express leptin receptors, leptin's effect on GnRH neurons must be indirect. Neurons within the hypothalamic arcuate nucleus that coexpress AGRP and NPY are considered to be important intermediate neurons involved in leptin regulation of GnRH neurons. Previously, we reported that the absence of AGRP and haploinsufficiency of MC4R in leptin receptor mutant (Lepr db/db ) females result in restoration of fertility and lactation despite the persistence of obesity and insulin resistance. The overarching hypothesis in the present study is that the absence or reduction of leptin's inhibition of AGRP/NPY neurons leads to suppression of GnRH release in cases of leptin signaling deficiency. Since TAC2 (NKB)-TAC3R signaling plays a role in puberty maturation and is modulated by metabolic status, the other aim of this study is to test whether TAC2/NKB neurons in ARC regulated by melanocortinergic signals herein affect leptin's action on puberty and reproduction. Our data showed that AGRP deficiency in Lepr db/db females restores normal timing of vaginal opening and estrous cycling, although uterine weight gain and mammary gland development are morphologically delayed. Nonetheless, Agrp Ϫ/Ϫ Lepr db/db females are fertile and sustain adequate nutrition of pups with lactation to weaning age. AGRP deficiency results in advanced vaginal opening in wild-type female mice. The postpubertal increase in hypothalamic TAC2 mRNA was not observed in Lepr db/db females, whereas AGRP deficiency restored it in Lepr db/db females. Additionally, MC4R activation with MTII induced FOS expression in TAC2 neurons, supporting the concept of melanocortinergic regulation of TAC2 neurons. These studies suggest that AGRP imposes an inhibitory effect on puberty and that TAC2 neurons may transmit melanocortinergic inhibition of GnRH neurons.agouti-related peptide; leptin; puberty; reproduction THE ONSET OF PUBERTY is the culmination of a subtle shift in balance of stimulatory and inhibitory neurotransmission within a complex neural network. Whereas the intrinsic pulsatility of GnRH neurons points toward a cell-autonomous function of gonadotropin-releasing hormone (GnRH) secretion, extrinsic signals are likely to be required to trigger activity in quiescent GnRH neurons. There is undoubtedly a link between metabolic status and GnRH activity (34). In the context of normal leptin signaling, a role has been implicated on the basis of a direct correlation between puberty onset and body weight (8, 16). Additionally, cases of defective leptin signaling in both humans and rodents result in hypogonadotropic hypogonadism (13). In a case report of a girl with leptin deficiency, treatment with leptin appeared to reverse the hypogonadal state (12). In cases of lipodystrophy with attendant hypoleptinemia, leptin therapy normalized pituitary hormone release (29) and restored menstrual cycles to all treat...

Dent disease, an X-linked recessive renal tubular disease, results from loss-of-function mutations in the CLCN5 chloride channel gene. The effects of Dent disease on growth have not been described. We report siblings who presented with proteinuria, calciuria, and phosphaturia and growth failure who responded to growth hormone (GH) treatment. Genotyping revealed a novel c.2179delG frameshift mutation at codon 727, exon 12 of the CLCNS gene. Two years after initial presentation, linear growth had slowed, and evaluation revealed isolated GH deficiency. GH therapy resulted in more than two-fold increases in height velocity and serum IGF-I levels. There was no net change in estimated glomerular filtration rate, proteinuria or calciuria in response to GH therapy, but there was a delayed improvement in phosphaturia. These cases provide insight into the effects of GH on growth and renal function in Dent disease. Furthermore, we have reported a novel CLCN5 mutation.

We report a case of a 14-year-old girl with primary amenorrhea and phenotypic as well as hormonal features of complete androgen insensitivity syndrome (CAIS), who tested positive for a novel missense androgen receptor gene mutation resulting in serine-to-isoleucine change at position 703 in exon 4 in the ligand-binding domain. The interesting features of this case include a persistence of Müllerian derivatives, Sertoli cell adenoma, Tanner III pubic hair, and a normal bone mineral density. These features are not typically described in CAIS. This novel mutation associated with a unique clinical presentation serves to significantly enrich the literature on this rare and fascinating disorder of androgen insensitivity syndrome.