A genetic basis for functional hypothalamic amenorrhea

Abstract

Background: Functional hypothalamic amenorrhea is a reversible form of gonadotropin-releasing hormone (GnRH) deficiency commonly triggered by stressors such as excessive exercise, nutritional deficits, or psychological distress. Women vary in their susceptibility to inhibition of the reproductive axis by such stressors, but it is unknown whether this variability reflects a genetic predisposition to hypothalamic amenorrhea. We hypothesized that mutations in genes involved in idiopathic hypogonadotropic hypogonadism, a congenital form of GnRH deficiency, are associated with hypothalamic amenorrhea.

Methods: We analyzed the coding sequence of genes associated with idiopathic hypogonadotropic hypogonadism in 55 women with hypothalamic amenorrhea and performed in vitro studies of the identified mutations.

Results: Six heterozygous mutations were identified in 7 of the 55 patients with hypothalamic amenorrhea: two variants in the fibroblast growth factor receptor 1 gene FGFR1 (G260E and R756H), two in the prokineticin receptor 2 gene PROKR2 (R85H and L173R), one in the GnRH receptor gene GNRHR (R262Q), and one in the Kallmann syndrome 1 sequence gene KAL1 (V371I). No mutations were found in a cohort of 422 controls with normal menstrual cycles. In vitro studies showed that FGFR1 G260E, FGFR1 R756H, and PROKR2 R85H are loss-of-function mutations, as has been previously shown for PROKR2 L173R and GNRHR R262Q.

Conclusions: Rare variants in genes associated with idiopathic hypogonadotropic hypogonadism are found in women with hypothalamic amenorrhea, suggesting that these mutations may contribute to the variable susceptibility of women to the functional changes in GnRH secretion that characterize hypothalamic amenorrhea. Our observations provide evidence for the role of rare variants in common multifactorial disease. (Funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development and others; ClinicalTrials.gov number, NCT00494169.).

Figures

Figure 1. Pedigrees of the Seven Patients with Hypothalamic Amenorrhea (HA) Found to Have Mutations

For each pedigree, the patient with the mutation is indicated by a red arrow. The mutated gene is indicated in bold to the left of the pedigree, and the allele status is given below the proband or affected family members, with plus signs indicating wild-type and G260E, R756H, R85H, L173R, R262Q, and V371I indicating the amino acid mutations. Squares indicate male family members, circles female family members, and diamonds offspring whose sex is not shown (with the numbers of persons given within the diamond).

Figure 2. Loss-of-Function Mutations in Patients with Hypothalamic Amenorrhea

Panels A and B show the structures of FGFR1 and PROKR2, respectively, as well as the mutations of interest. Panels C, D, and E show that the FGFR1 G260 and R756 amino acids and the PROKR2 R85 amino acid are highly conserved across vertebrate species. Panels F, G, and H show that the overall expression levels of FGFR1 G260E and R756H were normal, whereas PROKR2 R85H expression levels were decreased (P

Figure 3. Patterns of Luteinizing Hormone (LH) Secretion over a 24-Hour Period, According to Mutation Status

The pattern of LH secretion induced by endogenous gonadotropin-releasing hormone in the early follicular phase of the menstrual cycle is shown as a normal, pulsatile pattern in a healthy woman (Panel A), as apulsatile in a patient with hypothalamic amenorrhea and the FGFR1 R756H mutation (Panel B), and as both apulsatile and pulsatile with increasing amplitude during the night in a patient with the PROKR2 R85H mutation (Panel C). Arrowheads indicate peaks in secretion (of which there are none in the apulsatile pattern in Panel B). Mean levels of LH, follicle-stimulating hormone (FSH), and estradiol are listed for the two patients. To convert values for estradiol to picomoles per liter, multiply by 3.671.