Growth Hormone Deficiency in an Adolescent With Pseudohypoparathyroidism Type 1B

We report growth hormone (GH) deficiency due to presumed GH releasing hormone (GHRH) resistance in an adolescent with pseudohypoparathyroidism type 1B (PHP1B) due to paternal uniparental disomy of chromosome 20 (patUPD20). A male patient aged 11 years 10 months with obesity and mild developmental delay was found to have hypocalcemia, hyperphosphatemia, and an elevated parathyroid hormone level. History included muscle cramps and leg pain with activity. Examination showed round facies, short stature, and obesity. He was in puberty and bone age was advanced by > 2 years. Detailed genetic workup, including nucleotide sequence analysis of <i>GNAS</i> exons 1-13 and <i>STX16</i>, methylation-sensitive multiplex ligation-dependent probe amplification and analysis of several microsatellite markers for chromosome 20, established the diagnosis of PHP1B due to patUPD20. Muscle cramps and hypocalcemia resolved with calcium carbonate, ergocalciferol, and calcitriol treatment. He was short with linear growth deceleration at around age 13 years. Peak GH concentration was insufficient following stimulation testing. Growth velocity improved with human GH treatment. Although rare, resistance to GHRH can occur in PHP1B and patients with this disorder should be evaluated for GH insufficiency if they present with short stature and reduced growth velocity. Treatment with recombinant human GH may improve growth velocity in such patients.