One small study identified heterozygous mutations in the fibroblast growth factor receptor 1 gene FGFR, the prokineticin receptor 2 gene PROKR2, the hypothalamic gonadotrophin-releasing hormone receptor gene GNRHR, and the Kallmann syndrome 1 sequence gene KAL1 (27) in patients with FHA, suggesting an increased vulnerability to develop hypothalamic amenorrhea. This evidence concerns the gene PROKR2 and hypoalphalipoproteinemia, primary, 1.