Pediatric calcium disorders: hypoparathyroidism, rickets, XLH, bone health

Hypocalcemia and hypoparathyroidism

PTH raises calcium by releasing it from bone, by holding it in the kidney, and by stimulating renal 1α-hydroxylase to make calcitriol, which increases gut absorption. PTH also makes the kidney excrete phosphate. Without PTH, calcium falls and phosphate rises because the kidney excretes less phosphate.

• Signs: tetany, paresthesias, carpopedal spasm, Chvostek and Trousseau signs, laryngospasm, seizures, long QT.
• A PTH in the normal range is inappropriately normal when calcium is low and still means hypoparathyroidism.
• Neonate with hypocalcemic seizure, high phosphate and a conotruncal heart defect: think 22q11.2 deletion.
• Early neonatal hypocalcemia (first 72 hours): prematurity is the commonest cause; also infants of diabetic mothers and perinatal asphyxia.
• Late neonatal hypocalcemia (after day 3): transient hypoparathyroidism, often with a high phosphate load; also maternal hyperparathyroidism, maternal vitamin D deficiency and low magnesium.
• Also check magnesium: low magnesium blocks PTH release and action.

Treating hypoparathyroidism

• Seizure or tetany: IV calcium gluconate slowly with cardiac monitoring, then oral calcium plus calcitriol.
• Calcitriol, not plain vitamin D: without PTH the kidney cannot activate vitamin D through 1α-hydroxylase.
• Oral calcium carbonate both raises calcium and binds dietary phosphate.
• Infants: breast milk or a low-phosphate formula.
• Aim for calcium in the low-normal range. Pushing it to high-normal causes hypercalciuria, with nephrocalcinosis and kidney stones; monitor urine calcium.

Pseudohypoparathyroidism

In pseudohypoparathyroidism the kidney does not respond to PTH. Labs look like hypoparathyroidism, low calcium and high phosphate, but PTH is HIGH.

• Type 1a has Albright hereditary osteodystrophy: short stature, round face, obesity, short 4th and 5th metacarpals (missing knuckles on a fist), subcutaneous ossification.
• Cause: inactivating GNAS variants, autosomal dominant with imprinting. Inherited from the mother, they cause hormone resistance (PTH, and often TSH and gonadotropins).
• The same variant inherited from the father gives the AHO body features without hormone resistance (pseudopseudohypoparathyroidism).
• Treatment: calcium plus calcitriol as in hypoparathyroidism; screen for other hormone resistance, such as a high TSH.

Nutritional rickets

Rickets is failed mineralization at the growth plate. Nutritional rickets comes from too little vitamin D, too little calcium, or both.

• Labs: low 25-OH vitamin D, high PTH, high alkaline phosphatase; calcium low or normal, phosphate often low.
• Wrist or knee X-ray: widened, cupped and frayed metaphyses.
• Signs: bowed legs, widened wrists, rachitic rosary, delayed fontanelle closure, delayed walking.
• Treatment (global consensus 2016): vitamin D at least 2000 IU/day for at least 3 months, or one large dose, plus calcium 500 mg/day.
• Then prevention: 400 IU/day of vitamin D for infants, including all breastfed infants.

X-linked hypophosphatemia (XLH)

PHEX variants raise FGF23, which makes the kidney waste phosphate and keeps calcitriol inappropriately low. It is the commonest inherited rickets. It is X-linked dominant: an affected father passes it to all daughters and no sons.

• Treatment of choice in children (international guideline 2025): burosumab, an anti-FGF23 antibody, from 6 months of age.
• Oral phosphate with calcitriol is the alternative when burosumab is not available.
• Vitamin D alone does not heal XLH.

Hypercalcemia of immobilization

Prolonged immobilization, for example after a femur fracture, spinal cord injury or traction, speeds bone resorption. Growing adolescents with rapid bone turnover are most at risk.

• Symptoms: nausea, vomiting, constipation, weakness, polyuria and thirst, confusion.
• Labs: high calcium with suppressed PTH and high urine calcium.
• Treatment: IV fluids and mobilization as early as possible; bisphosphonates for severe or persistent cases.

Peak bone mass and bone health

Adult bone strength depends on the peak bone mass built in childhood. About 90% of peak bone mass is gained by about 18 years in girls and 20 years in boys, with the fastest gain around puberty, so adolescence is the key time for counseling.

• Builds bone: weight-bearing exercise and enough calcium and vitamin D (1300 mg calcium and 600 IU vitamin D a day for ages 9–18).
• Late puberty or hypogonadism lowers bone mineral density, because sex steroids drive accrual; so does energy deficiency (RED-S, anorexia nervosa).
• Chronic high-dose systemic glucocorticoids are the most harmful steroid exposure; usual inhaled corticosteroid doses have little effect on bone.
• Cigarette smoking is a bigger long-term bone threat than appropriately dosed inhaled steroids.

Common questions

Sources

• Second International Workshop 2022: Evaluation and management of hypoparathyroidism (J Bone Miner Res)
• International Working Group 2025: X-linked hypophosphatemia management in children (J Clin Endocrinol Metab)
• Global consensus 2016: Prevention and management of nutritional rickets (J Clin Endocrinol Metab)
• International consensus 2018: Diagnosis and management of pseudohypoparathyroidism (Nat Rev Endocrinol)
• AAP 2014: Optimizing bone health in children and adolescents (Pediatrics)

Written for Pedemy in our own words from the sources above; checked November 2026. For education only, not medical advice; check doses and local protocols before treating a patient. Pedemy is independent and not affiliated with or endorsed by the organizations cited.