PLOD1 and Primary amenorrhea: Herein, we hypothesized that biallelic GNRHR mutations could be enriched among adolescent and young adult females presenting with clinical and biochemical signs suggesting partial gonadotropin deficiency, and found statistical evidence to support this notion, since two patients in our series of nine harbored biallelic mutations in GNRHR. The patient harboring a compound heterozygous GNRHR mutation p.(Gln106Arg) and p.(Phe309del) had spontaneous breast development, primary amenorrhea, low estradiol levels with low-normal gonadotropin levels and normal pubertal LH response to GnRH stimulation.