Andrew Dwyer

Human GnRH Deficiency: A Unique Disease Model to Unravel the Ontogeny of GnRH Neurons

Evolutionary survival of a species is largely a function of its reproductive fitness. In mammals, a sparsely populated and widely dispersed network of hypothalamic neurons, the gonadotropin-releasing hormone (GnRH) neurons, serve as the pilot light of reproduction via coordinated secretion of GnRH. Since it first description, human GnRH deficiency has been recognized both clinically and genetically as a heterogeneous disease. A spectrum of different reproductive phenotypes comprised of congenital GnRH deficiency with anosmia (Kallmann syndrome), congenital GnRH deficiency with normal olfaction (normosmic idiopathic hypogonadotropic hypogonadism), and adult-onset hypogonadotropic hypogonadism has been described. In the last two decades, several genes and pathways which govern GnRH ontogeny have been discovered by studying humans with GnRH deficiency. More importantly, detailed study of these patients has highlighted the emerging theme of oligogenicity and genotypic synergism, and also expanded the phenotypic diversity with the documentation of reversal of GnRH deficiency later in adulthood in some patients. The underlying genetic defect has also helped understand the associated nonreproductive phenotypes seen in some of these patients. These insights now provide practicing clinicians with targeted genetic diagnostic strategies and also impact on clinical management.

Transition of Care from Childhood to Adulthood: Congenital Hypogonadotropic Hypogonadism

Passage from childhood to adult life involves biological changes culminating in full reproductive capacity as well as psychosocial development. For patients with congenital hypogonadotropic hypogonadism (CHH), this can be an emotionally challenging time as their pubertal failure results in striking physical differences from their peers. CHH is difficult to differentiate from common disorders of puberty such as constitutional delay of growth and puberty. As such, delays in diagnosis are frequent, and it is a common source of stress and frustration for these adolescents. While effective treatments are available for inducing puberty and attaining fertility is possible in most cases, patients may find it difficult to cope with living with CHH. A critical issue for adolescents with CHH is the risk for being lost to follow-up during the transition from pediatric-centered care to adult care. This article will review the state of the art in diagnosis and treatment of patients with CHH with a particular focus on supporting an effective transition from pediatric-centered care to adult-oriented endocrine services. A synthesis of best practices is offered to help guide clinicians in supporting patients and families during this challenging period of care.