Few PHP1B patients with partial or unquantified growth hormone (GH) deficiency due to presumed GH releasing hormone (GHRH) resistance have been described, including 2 patients with PHP1B due to methylation defects affecting all differentially methylated regions (DMRs) at the GNAS locus and monozygotic twins with autosomal dominant PHP1B (AD-PHP1B) due to a STX16 microdeletion (3-5). The gene discussed is GNAS; the disease is pseudohypoparathyroidism type 1B.