A review of Kallmann syndrome: genetics, pathophysiology, and clinical management

KNDy neurones and GnRH/LH pulse generation: Current understanding and future aspects

Uncovering the central mechanism underlying mammalian reproduction is warranted to develop new therapeutic approaches for reproductive disorders in humans and domestic animals. The present study focused on the role of arcuate kisspeptin neurones (also known as KNDy neurones) as an intrinsic gonadotropin-releasing hormone (GnRH) pulse generator, which plays a fundamental role in mammalian reproduction via the stimulation of pituitary gonadotropin synthesis and release and thereby in gametogenesis and steroidogenesis in the gonads of mammals. We also discuss the mechanism that inhibits pulsatile GnRH/gonadotropin release under a negative energy balance, considering that reproductive disorders often occur during malnutrition in humans and livestock.

Mechanisms of Central Hypogonadism

Reproductive function depends upon an operational hypothalamo–pituitary–gonadal (HPG) axis. Due to its role in determining survival versus reproductive strategies, the HPG axis is vulnerable to a diverse plethora of signals that ultimately manifest with Central Hypogonadism (CH) in all its many guises. Acquired CH can result from any pituitary or hypothalamic lesion, including its treatment (such as surgical resection and/or radiotherapy). The HPG axis is particularly sensitive to the suppressive effects of hyperprolactinaemia that can occur for many reasons, including prolactinomas, and as a side effect of certain drug therapies. Physiologically, prolactin (combined with the suppressive effects of autonomic neural signals from suckling) plays a key role in suppressing the gonadal axis and establishing temporary CH during lactation. Leptin is a further key endocrine regulator of the HPG axis. During starvation, hypoleptinaemia (from diminished fat stores) results in activation of hypothalamic agouti-related peptide neurons that have a dual purpose to enhance appetite (important for survival) and concomitantly suppresses GnRH neurons via effects on neural kisspeptin release. Obesity is associated with hyperleptinaemia and leptin resistance that may also suppress the HPG axis. The suppressibility of the HPG axis also leaves it vulnerable to the effects of external signals that include morphine, anabolic-androgenic steroids, physical trauma and stress, all of which are relatively common causes of CH. Finally, the HPG axis is susceptible to congenital malformations, with reports of mutations within >50 genes that manifest with congenital CH, including Kallmann Syndrome associated with hyposmia or anosmia (reduction or loss of the sense of smell due to the closely associated migration of GnRH with olfactory neurons during embryogenesis). Analogous to the HPG axis itself, patients with CH are often vulnerable, and their clinical management requires both sensitivity and empathy.

Kallman syndrome and central non-obstructive azoospermia

The understanding of male factors of infertility has grown exponentially in the past ten years. While clear guidelines for obstructive azoospermia have been developed, management of non-obstructive azoospermia has lagged. Specifically, management of Kallmann Syndrome and central non-obstructive azoospermia has been limited by a lack of understanding of the molecular pathogenesis and investigational trials exploring the best option for management and fertility in these patients. This review aims to summarize our current understanding of the causes of central hypogonadotropic hypogonadism with a focus on genetic etiologies while also discussing options that endocrinologists and urologists can utilize to successfully treat this group of infertile men.

Fezf1 is a novel regulator of female sex behavior in mice

Female sexual behavior is a complex process regulated by multiple brain circuits and influenced by sex steroid hormones acting in the brain. Several regions in the hypothalamus have been implicated in the regulation of female sexual behavior although a complete circuitry involved in female sexual behavior is not understood. Fez family zinc finger 1 (Fezf1) gene is a brain specific gene that has been mostly studied in the context of olfactory development, although in a recent study, FEZF1 has been identified as one of the genes responsible for the development of Kallman syndrome. In the present study, we utilized shRNA approach to downregulate Fezf1 in the ventromedial nucleus of the hypothalamus (VMN) with the aim to explore the role of this gene. Adult female mice were stereotaxically injected with lentiviral vectors encoding shRNA against Fezf1 gene. Mice injected with shRNA against Fezf1 had significantly reduced female sexual behavior, presumably due to the downregulation of estrogen receptor alpha (ERα), as the number of ERα-immunoreactive cells in the VMN of Fezf1 mice was significantly lower in comparison to controls. However, no effect on body weight or physical activity was observed in mice with downregulated Fezf1, suggesting that the role of Fezf1 in the VMN is limited to the regulation of sexual behavior.

SIGNIFICANCE STATEMENT

Fezf1 gene has been identified in the present study as a regulator of female sexual behavior in mice. Regulation of the female sexual behavior could be through the regulation of estrogen receptor alpha expression in the ventromedial nucleus of the hypothalamus, as the expression of this receptor was reduced in mice with downregulated Fezf1. As expression of Fezf1 is very specific in the brain, this gene could present a potential target for the development of novel drugs regulating hypoactive sexual desire disorder in women, if similar function of FEZF1 will be confirmed in humans.

Clinical characteristics of 138 Chinese female patients with idiopathic hypogonadotropic hypogonadism

OBJECTIVE

To evaluate the clinical features of Chinese women with idiopathic hypogonadotropic hypogonadism (IHH).

METHODS

We retrospectively reviewed the clinical characteristics, laboratory and imaging findings, therapeutic management and fertility outcomes of 138 women with IHH. All patients had been treated and followed up at an academic medical centre during 1990-2016.

RESULTS

Among the 138 patients, 82 patients (59.4%) were diagnosed with normosmic IHH and 56 patients (40.6%) were diagnosed with Kallmann syndrome (KS). The patients with IHH experienced occasional menses (4.3%), spontaneous thelarche (45.7%) or spontaneous pubarche (50.7%). Women with thelarche had a higher percentage of pubarche (P  < 0.001) and higher gonadotropin concentrations (P  < 0.01). Olfactory bulb/sulci abnormalities were found during the magnetic resonance imaging (MRI) of all patients with KS. Most patients with IHH had osteopenia and low bone age. Among the 16 women who received gonadotropin-releasing hormone treatment, ovulation induction or assisted reproductive technology, the clinical pregnancy rate was 81.3% and the live birth rate was 68.8%.

CONCLUSIONS

The present study revealed that the phenotypic spectrum of women with IHH is broader than typical primary amenorrhoea with no secondary sexual development, including occasional menses, spontaneous thelarche or pubarche. MRI of the olfactory system can facilitate the diagnosis of KS. Pregnancy can be achieved after receiving appropriate treatment.

Sexuality and quality of life in congenital hypogonadisms

Turner syndrome and idiopathic congenital hypogonadism including Kallmann syndrome are conditions associated to a large number of widely known comorbidities that need a medical support forever. One of the characteristics shared by both conditions is the lack of sexual development that influencing the sexuality functioning and quality of life of the affected women. Few studies have been conducted to assess these topics, but they need to be considered in the treatment to all women with hypogonadism. This review on the major medical issues and psychological aspects, also focus in the present knowledge about sexual function and quality of life of women with Turner syndrome and idiopathic congenital hypogonadism, which aims to help in the comprehensive management of these patients.

Arachnoid cyst: a further anomaly associated with Kallmann syndrome?

BACKGROUND

Kallmann syndrome (KS) is defined by the association of hypogonadotropic hypogonadism and anosmia. It is characterized by a significant clinical and genetic heterogeneity; actually, it may present several non-reproductive non-olfactory anomalies, and all the ways of genetic transmission can be involved in the inheritance of the disease. Although six pathogenesis-related genes have been identified so far, KS remains sporadic in 70 % of the cases, and the genetic diagnosis is not available for all of them. The purpose of this paper is to present a further disease that can enrich the wide spectrum of KS variability, that is cerebral arachnoid cyst.

CASE DESCRIPTION

This 11-year-old boy presented with the typical characteristics of KS together with those related to a sylvian arachnoid cyst. He was admitted because of worsening headache. At the admission, the physical examination revealed eunuchoid aspect, micropenis, previous cryptorchidism, and anosmia. MRI pointed out a large, left sylvian arachnoid cyst, agenesia of the olfactory bulbs/tracts complex, and hypoplasia of the left olfactory sulcus. The child was operated on by endoscopic fenestration of the cyst, followed by transient external drainage for subdural hygroma and microscopic fenestration for recurrence of the cyst. His statural growth is normal but the sexual development still delayed in spite of hormone replacement therapy.

CONCLUSION

According to the present and the other four cases in the literature, arachnoid cyst should be included among the anomalies possibly accompanying KS date although this association seems to be occasional as far as embryogenesis and physiopathology are concerned.

Congenital Hypogonadotropic Hypogonadism and Kallmann Syndrome: Past, Present, and Future

The proper development and coordination of the hypothalamic-pituitary-gonadal (HPG) axis are essential for normal reproductive competence. The key factor that regulates the function of the HPG axis is gonadotrophin-releasing hormone (GnRH). Timely release of GnRH is critical for the onset of puberty and subsequent sexual maturation. Misregulation in this system can result in delayed or absent puberty and infertility. Congenital hypogonadotropic hypogonadism (CHH) and Kallmann syndrome (KS) are genetic disorders that are rooted in a GnRH deficiency but often accompanied by a variety of non-reproductive phenotypes such as the loss of the sense of smell and defects of the skeleton, eye, ear, kidney, and heart. Recent progress in DNA sequencing technology has produced a wealth of information regarding the genetic makeup of CHH and KS patients and revealed the resilient yet complex nature of the human reproductive neuroendocrine system. Further research on the molecular basis of the disease and the diverse signal pathways involved will aid in improving the diagnosis, treatment, and management of CHH and KS patients as well as in developing more precise genetic screening and counseling regime.

Mutation analyses in pedigrees and sporadic cases of ethnic Han Chinese Kallmann syndrome patients

Kallmann syndrome, a form of idiopathic hypogonadotropic hypogonadism, is characterized by developmental abnormalities of the reproductive system and abnormal olfaction. Despite association of certain genes with idiopathic hypogonadotropic hypogonadism, the genetic inheritance and expression are complex and incompletely known. In the present study, seven Kallmann syndrome pedigrees in an ethnic Han Chinese population were screened for genetic mutations. The exons and intron-exon boundaries of 19 idiopathic hypogonadotropic hypogonadism (idiopathic hypogonadotropic hypogonadism)-related genes in seven Chinese Kallmann syndrome pedigrees were sequenced. Detected mutations were also tested in 70 sporadic Kallmann syndrome cases and 200 Chinese healthy controls. In pedigrees 1, 2, and 7, the secondary sex characteristics were poorly developed and the patients' sense of smell was severely or completely lost. We detected a genetic mutation in five of the seven pedigrees: homozygous KAL1 p.R191ter (pedigree 1); homozygous KAL1 p.C13ter (pedigree 2; a novel mutation); heterozygous FGFR1 p.R250W (pedigree 3); and homozygous PROKR2 p.Y113H (pedigrees 4 and 5). No genetic change of the assayed genes was detected in pedigrees 6 and 7. Among the 70 sporadic cases, we detected one homozygous and one heterozygous PROKR2 p.Y113H mutation. This mutation was also detected heterozygously in 2/200 normal controls and its pathogenicity is likely questionable. The genetics and genotype-phenotype relationships in Kallmann syndrome are complicated. Classical monogenic inheritance does not explain the full range of genetic inheritance of Kallmann syndrome patients. Because of stochastic nature of genetic mutations, exome analyses of Kallmann syndrome patients may provide novel insights.

A novel nonsense mutation of the KAL1 gene (p.Trp204*) in Kallmann syndrome

Objective

To describe a novel KAL1 mutation in patients affected by Kallmann syndrome.

Setting

Endocrinology Clinic of the João de Barros Barreto University Hospital – Federal University of Pará, Brazil.

Methods

Clinical examination, hormone assays and sequencing of exons 5, 6 and 9 of the KAL1 gene in four Brazilian brothers with Kallmann syndrome.

Results

Detected a novel KAL1 mutation, c.612G.A/p.Trp204*, in four hemizygous brothers with Kallmann syndrome, and five heterozygous female family members.

Conclusion

The novel p.Trp204* mutation of the KAL1 gene results in the production of a truncated anosmin-1 enzyme in patients with Kallmann syndrome. This finding broadens the spectrum of pathogenic mutations for this disease.

The olfactory system as the gateway to the neural correlates of consciousness

How consciousness is generated by the nervous system remains one of the greatest mysteries in science. Investigators from diverse fields have begun to unravel this puzzle by contrasting conscious and unconscious processes. In this way, it has been revealed that the two kinds of processes differ in terms of the underlying neural events and associated cognitive mechanisms. We propose that, for several reasons, the olfactory system provides a unique portal through which to examine this contrast. For this purpose, the olfactory system is beneficial in terms of its (a) neuroanatomical aspects, (b) phenomenological and cognitive/mechanistic properties, and (c) neurodynamic (e.g., brain oscillations) properties. In this review, we discuss how each of these properties and aspects of the olfactory system can illuminate the contrast between conscious and unconscious processing in the brain. We conclude by delineating the most fruitful avenues of research and by entertaining hypotheses that, in order for an olfactory content to be conscious, that content must participate in a network that is large-scale, both in terms of the neural systems involved and the scope of information integration.

The development of kisspeptin circuits in the Mammalian brain

The neuropeptide kisspeptin, encoded by the Kiss1 gene, is required for mammalian puberty and fertility. Examining the development of the kisspeptin system contributes to our understanding of pubertal progression and adult reproduction and sheds light on possible mechanisms underlying the development of reproductive disorders, such as precocious puberty or hypogonadotropic hypogonadism. Recent work, primarily in rodent models, has begun to study the development of kisspeptin neurons and their regulation by sex steroids and other factors at early life stages. In the brain, kisspeptin is predominantly expressed in two areas of the hypothalamus, the anteroventral periventricular nucleus and neighboring periventricular nucleus (pre-optic area in some species) and the arcuate nucleus. Kisspeptin neurons in these two hypothalamic regions are differentially regulated by testosterone and estradiol, both in development and in adulthood, and also display differences in their degree of sexual dimorphism. In this chapter, we discuss what is currently known and not known about the ontogeny, maturation, and sexual differentiation of kisspeptin neurons, as well as their regulation by sex steroids and other factors during development.

Male reprotoxicity and endocrine disruption

Mammalian reproductive tract development is a tightly regulated process that can be disrupted following exposure to drugs, toxicants, endocrine-disrupting chemicals (EDCs), or other compounds via alterations to gene and protein expression or epigenetic regulation. Indeed, the impacts of developmental exposure to certain toxicants may not be fully realized until puberty or adulthood when the reproductive tract becomes sexually mature and altered functionality is manifested. Exposures that occur later in life, once development is complete, can also disrupt the intricate hormonal and paracrine interactions responsible for adult functions, such as spermatogenesis. In this chapter, the biology and toxicology of the male reproductive tract is explored, proceeding through the various life stages including in utero development, puberty, adulthood, and senescence. Special attention is given to the discussion of EDCs, chemical mixtures, low-dose effects, transgenerational effects, and potential exposure-related causes of male reproductive tract cancers.

BAX-dependent and BAX-independent regulation of Kiss1 neuron development in mice

The Kiss1 gene and its product kisspeptin are important regulators of reproduction. In rodents, Kiss1 is expressed in the hypothalamic arcuate (ARC) and anteroventral periventricular (AVPV)/rostral periventricular (PeN) nuclei. In the AVPV/PeN, females have more Kiss1 and tyrosine hydroxylase (TH) neurons than males. We explored the ontogeny of the Kiss1 sex difference, and the role of cell death in establishing Kiss1 and TH cell number. We also determined whether Kiss1 cells in AVPV/PeN coexpress TH. AVPV/PeN Kiss1 neurons were first detected in both sexes on postnatal d 10, but the Kiss1 sex difference did not emerge until postnatal d 12. The role of BAX-mediated apoptosis in generating this sex difference was tested in adult Bax knockout (KO) and wild-type mice. Deletion of Bax did not diminish the sex difference in Kiss1 expression in the AVPV/PeN. TH expression was sexually dimorphic in the AVPV of both wild-type and Bax KO mice but, unlike Kiss1, was not sexually dimorphic in the PeN of either genotype. Double-label analysis determined that most Kiss1 neurons coexpress TH mRNA, but many TH neurons do not coexpress Kiss1, especially in the PeN. These findings suggest that several subpopulations of TH cells reside within the AVPV/PeN, only one of which coexpresses Kiss1. In the ARC, Kiss1 cell number was markedly increased in Bax KO mice of both sexes, indicating that although BAX-dependent apoptosis does not generate the sex difference in either Kiss1 or TH expression in AVPV/PeN, BAX does importantly regulate Kiss1 cell number in the ARC.

Hypoestrogenism in young women and its influence on bone mass density

One of the most important hormonal factors responsible for bone health is estradiol. Genetic factors, adequacy of hormonal functioning, nutrition and physical activity may be the markers of bone status and development in young women. During adolescence, women reach peak bone acquisition and develop a skeletal mass. This process is largely regulated by endocrine factors mainly such as adequate levels of gonadal, adrenal and pituitary hormones. The crucial role played by estradiol and its impact on bones are very multiple. Estradiol induces growth factors' activation, receptor activator of nuclear factor kappa B ligand (RANKL) production inhibition and is mainly referred to antiresorptive activity. Clinical situations leading to hypoestrogenism has been linked to decreased bone mineral density leading to osteopenia and osteoporosis. This status both in fertile and perimenopausal women can increase the risk of pathological fractures. Such conditions as hypothalamic-pituitary insufficiency (functional hypothalamic amenorrhea, anorexia nervosa, Kallmann syndrome, hyperprolactinemia), ovarian failure (gonadal dysgenesis, premature ovarian failure) and iatrogenic treatment (surgery, chemotherapy, radiotherapy) can cause hypoestrogenism. The treatment of osteopenia and osteoporosis caused by hypoestrogenism is very essential and multidirectional. The crucial role of the therapy is the achievement of proper serum estradiol concentration and eliminate the causes of hypoestrogenism.

Coming of age in the kisspeptin era: sex differences, development, and puberty

The status of the neuroendocrine reproductive axis differs dramatically during various stages of development, and also differs in several critical ways between the sexes, including its earlier pubertal activation in females than males and the presence of neural circuitry that generates preovulatory hormone surges in females but not males. The reproductive axis is controlled by various hormonal and neural pathways that converge upon forebrain gonadotropin-releasing hormone (GnRH) neurons, and many of the critical age and sex differences in the reproductive axis likely reflect differences in the "upstream" circuits and factors that regulate the GnRH system. Recently, the neural kisspeptin system has been implicated as an important regulator of GnRH neurons. Here I discuss the evidence supporting a critical role of kisspeptin signaling at different stages of life, including early postnatal and pubertal development, as well as in adulthood, focusing primarily on information gleaned from mammalian studies. I also evaluate key aspects of sexual differentiation and development of the brain as it relates to the Kiss1 system, with special emphasis on rodents. In addition to discussing recent advances in the field of kisspeptin biology, this paper will highlight a number of unanswered questions and future challenges for kisspeptin investigators, and will stress the importance of studying the kisspeptin system in both males and females, as well as in multiple species.

Cleft lip and palate results from Hedgehog signaling antagonism in the mouse: Phenotypic characterization and clinical implications

BACKGROUND

The Hedgehog (Hh) pathway provides inductive signals critical for developmental patterning of the brain and face. In humans and in animal models interference with this pathway yields birth defects, among the most well-studied of which fall within the holoprosencephaly (HPE) spectrum.

METHODS

Timed-pregnant C57Bl/6J mice were treated with the natural Hh signaling antagonist cyclopamine by subcutaneous infusion from gestational day (GD) 8.25 to 9.5, or with a potent cyclopamine analog, AZ75, administered by oral gavage at GD 8.5. Subsequent embryonic morphogenesis and fetal central nervous system (CNS) phenotype were respectively investigated by scanning electron microscopy and high resolution magnetic resonance imaging (MRI).

RESULTS

In utero Hh signaling antagonist exposure induced a spectrum of craniofacial and brain malformations. Cyclopamine exposure caused lateral cleft lip and palate (CLP) defects attributable to embryonic deficiency of midline and lower medial nasal prominence tissue. The CLP phenotype was accompanied by olfactory bulb hypoplasia and anterior pituitary aplasia, but otherwise grossly normal brain morphology. AZ75 exposure caused alobar and semilobar HPE with associated median facial deficiencies. An intermediate phenotype of median CLP was produced infrequently by both drug administration regimens.

CONCLUSIONS

The results of this study suggest that interference with Hh signaling should be considered in the CLP differential and highlight the occurrence of CNS defects that are expected to be present in a cohort of patients having CLP. This work also illustrates the utility of fetal MRI-based analyses and establishes a novel mouse model for teratogen-induced CLP.

Human olfaction: a constant state of change-blindness

Paradoxically, although humans have a superb sense of smell, they don’t trust their nose. Furthermore, although human odorant detection thresholds are very low, only unusually high odorant concentrations spontaneously shift our attention to olfaction. Here we suggest that this lack of olfactory awareness reflects the nature of olfactory attention that is shaped by the spatial and temporal envelopes of olfaction. Regarding the spatial envelope, selective attention is allocated in space. Humans direct an attentional spotlight within spatial coordinates in both vision and audition. Human olfactory spatial abilities are minimal. Thus, with no olfactory space, there is no arena for olfactory selective attention. Regarding the temporal envelope, whereas vision and audition consist of nearly continuous input, olfactory input is discreet, made of sniffs widely separated in time. If similar temporal breaks are artificially introduced to vision and audition, they induce “change blindness”, a loss of attentional capture that results in a lack of awareness to change. Whereas “change blindness” is an aberration of vision and audition, the long inter-sniff-interval renders “change anosmia” the norm in human olfaction. Therefore, attentional capture in olfaction is minimal, as is human olfactory awareness. All this, however, does not diminish the role of olfaction through sub-attentive mechanisms allowing subliminal smells a profound influence on human behavior and perception.

Gonadal and nongonadal regulation of sex differences in hypothalamic Kiss1 neurones

The brains of males and females differ anatomically and physiologically, including sex differences in neurone size or number, synapse morphology and specific patterns of gene expression. Brain sex differences may underlie critical sex differences in physiology or behaviour, including several aspects of reproduction, such as the timing of sexual maturation (earlier in females than males) and the ability to generate a preovulatory gonadotrophin surge (in females only). The reproductive axis is controlled by afferent pathways that converge upon forebrain gonadotrophin-releasing hormone (GnRH) neurones, but GnRH neurones are not sexually dimorphic. Although most reproductive sex differences probably reflect sex differences in the upstream circuits and factors that regulate GnRH secretion, the key sexually-dimorphic factors that influence reproductive status have remained poorly defined. The recently-identified neuropeptide kisspeptin, encoded by the Kiss1 gene, is an important regulator of GnRH secretion, and Kiss1 neurones in rodents are sexually dimorphic in specific hypothalamic populations, including the anteroventral periventricular nucleus-periventricular nucleus continuum (AVPV/PeN) and the arcuate nucleus (ARC). In the adult AVPV/PeN, Kiss1 neurones are more abundant in females than males, representing a sex difference that is regulated by oestradiol signalling during critical periods of postnatal and pubertal development. By contrast, Kiss1 neurones in the ARC are not sexually differentiated in adult rodents but, in mice, the regulation of ARC Kiss1 cells by gonadal hormone-independent factors is sexually dimorphic during prepubertal development. These various sex differences in hypothalamic Kiss1 neurones may relate to known sex differences in reproductive physiology, such as puberty onset and positive feedback.

When size matters: a clinical review of pathological micropenis

Micropenis is a significantly small penis with normal internal male genitalia. Micropenis is usually diagnosed shortly after birth, and the cause should be established; in addition, it should be differentiated from other associated syndromes. The role of the pediatric nurse practitioner is to diagnose the micropenis, guide the parents through the options of management, and support all involved through the selected treatment, whether hormonal or surgical. Patients affected with micropenis will need long-term management from their pediatric nurse practitioners, as well as follow-up by endocrinologists, urologists, pediatric surgeons (if surgery is chosen as the treatment), psychologists, and social workers. The need of more long-term research on patients with micropenis also is discussed.

Sexual differentiation and development of forebrain reproductive circuits

Males and females exhibit numerous anatomical and physiological differences in the brain that often underlie important sex differences in physiology or behavior, including aspects relating to reproduction. Neural sex differences are both region-specific and trait-specific and may consist of divergences in synapse morphology, neuron size and number, and specific gene expression levels. In most cases, sex differences are induced by the sex steroid hormonal milieu during early perinatal development. In rodents, the hypothalamic anteroventral periventricular nucleus (AVPV) is sexually differentiated as a result of postnatal sex steroids, and also specific neuronal populations in this nucleus are sexually dimorphic, with females possessing more kisspeptin, dopaminergic, and GABA/glutamate neurons than males. The ability of female rodents, but not males, to display an estrogen-induced luteinizing hormone (LH) surge is consistent with the higher levels of these neuropeptides in the AVPV of females. Of these AVPV populations, the recently identified kisspeptin system has been most strongly implicated as a crucial component of the sexually dimorphic LH surge mechanism, though GABA and glutamate have also received some attention. New findings have suggested that the sexual differentiation and development of kisspeptin neurons in the AVPV is mediated by developmental estradiol signaling. Although apoptosis is the most common process implicated in neuronal sexual differentiation, it is currently unknown how developmental estradiol acts to differentiate specific neuronal populations in the AVPV, such as kisspeptin or dopaminergic neurons.

Molecular pathology of the fibroblast growth factor family

The human fibroblast growth factor (FGF) family contains 22 proteins that regulate a plethora of physiological processes in both developing and adult organism. The mutations in the FGF genes were not known to play role in human disease until the year 2000, when mutations in FGF23 were found to cause hypophosphatemic rickets. Nine years later, seven FGFs have been associated with human disorders. These include FGF3 in Michel aplasia; FGF8 in cleft lip/palate and in hypogonadotropic hypogonadism; FGF9 in carcinoma; FGF10 in the lacrimal/salivary glands aplasia, and lacrimo-auriculo-dento-digital syndrome; FGF14 in spinocerebellar ataxia; FGF20 in Parkinson disease; and FGF23 in tumoral calcinosis and hypophosphatemic rickets. The heterogeneity in the functional consequences of FGF mutations, the modes of inheritance, pattern of involved tissues/organs, and effects in different developmental stages provide fascinating insights into the physiology of the FGF signaling system. We review the current knowledge about the molecular pathology of the FGF family.

Molecular analysis of KAL-1 in a series of Kallmann syndrome and normosmic idiopathic hypogonadotropic hypogonadism patients from Northwestern China

We conducted an analysis of the Kallmann syndrome 1 (KAL-1) genotype in 17 patients with Kallmann syndrome (KS), 9 patients with normosmic idiopathic hypogonadotropic hypogonadism (nIHH) and 20 age-matched normal men in Northwestern China. To do this, we used multiplex PCR analysis with exon-flanking primers and automated sequencing techniques with peripheral blood DNA samples. Intragenic deletions were found at the KAL-1 locus in two KS patients. One case with an atrial septal defect exhibited an intragenic deletion of exon 6. Another KS patient with cryptorchidism had intragenic deletions of exons 5 and 6. For the nIHH patients, no abnormalities were observed in the exonic and flanking sequences of KAL-1. This report describes two intragenic deletions of KAL-1 in two KS patients and suggests that KAL-1 deletion might be more prevalent in KS patients with other congenital organ abnormalities than those described previously in other series from Northwestern China.

Disorders of pubertal development

BACKGROUND

Puberty is an extremely important phase in the physical and psychosocial development of the adolescent.

METHODS

Selective literature review.

RESULTS

The diagnosis of abnormal puberty requires thorough knowledge of normal pubertal development and of the variations of normal puberty as well as its pathology. Variations of normal pubertal development can be expected, by definition, to occur at a frequency of roughly 3%. A detailed history is the first step in the diagnostic evaluation of a normal variant or an abnormal puberty. Further evaluation includes laboratory testing (estradiol, testosterone, and the results of a GnRH test, among others) and imaging studies (x-ray of the left hand and wrist, ultrasonography of the gonads, magnetic resonance imaging). Treatment is directed at both the acute and the long-term consequences of precocious, markedly delayed, or absent pubertal development.

CONCLUSIONS

Disorders of pubertal development should be recognized early, correctly diagnosed by a pediatric endocrinologist, and appropriately treated.

Human olfaction: from genomic variation to phenotypic diversity

The sense of smell is a complex molecular device, encompassing several hundred olfactory receptor proteins (ORs). These receptors, encoded by the largest human gene superfamily, integrate odorant signals into an accurate 'odor image' in the brain. Widespread phenotypic diversity in human olfaction is, in part, attributable to prevalent genetic variation in OR genes, owing to copy number variation, deletion alleles and deleterious single nucleotide polymorphisms. The development of new genomic tools, including next generation sequencing and CNV assays, provides opportunities to characterize the genetic variations of this system. The advent of large-scale functional screens of expressed ORs, combined with genetic association studies, has the potential to link variations in ORs to human chemosensory phenotypes. This promises to provide a genome-wide view of human olfaction, resulting in a deeper understanding of personalized odor coding, with the potential to decipher flavor and fragrance preferences.