title: Parathyroid hormone reserve in 22q11.2 deletion syndrome.
abstract: OBJECTIVE
  We hypothesized that most patients with 22q11.2 deletion and a history of hypocalcemia have inadequate parathyroid function, manifested by intact parathyroid hormone levels below normal. We aimed to evaluate intact parathyroid hormone levels both during normocalcemia and at hypocalcemia, in this population.
  
  
  METHODS
  Retrospective chart review of 103 patients with 22q11.2 deletion born since 1997 and cared for at the Children's Hospital of Philadelphia. Calcium and intact parathyroid hormone drawn simultaneously were recorded, along with clinical presentation at hypocalcemia.
  
  
  RESULTS
  Forty-seven simultaneous Ca/intact parathyroid hormone values were available. Seventy-nine percent of calcium levels and 81% of parathyroid hormone levels were within normal range. There were 19 patients with a history of symptomatic hypocalcemia, for whom any available simultaneous Ca/parathyroid hormone levels, before, during, or after hypocalcemia were analyzed. In this subgroup, 59% of calcium and 76% of parathyroid hormone levels were normal. None had an intact parathyroid hormone of >39.2 pg/mL at hypocalcemia. Seventy-three percent of hypocalcemic events had a precipitating stressor.
  
  
  CONCLUSIONS
  Hypoparathyroidism in 22q11.2 deletion is mild, manifesting as a phenomenon of decreased parathyroid hormone reserve. Subjects are normocalcemic most of the time, but are unable to mount elevated intact parathyroid hormone levels, and therefore unable to correct hypocalcemia, in response to stressors.
authors.affiliation: Division of Endocrinology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA. kapadiac@email.chop.edu
authors.forename: Chirag R
authors.initials: CR
authors.lastname: Kapadia
authors.forename: Yuran E
authors.initials: YE
authors.lastname: Kim
authors.forename: Donna M
authors.initials: DM
authors.lastname: McDonald-McGinn
authors.forename: Elaine H
authors.initials: EH
authors.lastname: Zackai
authors.forename: Lorraine E Levitt
authors.initials: LE
authors.lastname: Katz
mesh_terms: D002118:Calcium / Q000097:blood; D002648:Child; D002675:Child, Preschool; D002872:Chromosome Deletion; D002892:Chromosomes, Human, Pair 22; D006801:Humans; D010281:Parathyroid Hormone / Q000097:blood*
chemical_list: D010281:Parathyroid Hormone; D002118:Calcium