PTH and Hypocalcemia: In patients with PHP‐1a, resistance to PTH is usually absent at birth and evolves over time (from the neonatal period to 22 years); the first biochemical abnormalities to appear are increased serum PTH and phosphorous levels, whereas hypocalcemia develops gradually 4–5 years later9 which explains the normality of serum calcium level during the initial etiological investigation of our patient at the age of 15 years.