Gonadotropin-releasing hormone deficiency Gonadotropin-releasing hormone (GnRH) deficiency (IGD) is characterized by inappropriately low serum concentrations of the gonadotropins LH (luteinizing hormone) and FSH (follicle-stimulating hormone) in the presence of low circulating concentrations of sex steroids (primarily testosterone or estradiol). GnRH is not typically assayed directly because it is released in pulses from the hypothalamus, and its concentration can fluctuate rapidly and in a complex pattern that makes single blood measurements less informative than the pituitary's response. Hypothalamic GNRH deficiency Hypothalamic gonadotropin-releasing hormone deficiency UMLS:C4025644 HP:0003164 Abnormal hypothalamus physiology Abnormal gonadotropin-releasing hormone concentration