Evaluation of parathyroid gland function using sodium bicarbonate infusion test for 22q11.2 deletion syndrome.
OBJECTIVE
22q11.2 Deletion syndrome is a congenital malformation syndrome with hypoparathyroidism. The spectrum of parathyroid gland dysfunction ranges from severe neonatal hypocalcemia to subclinical hypoparathyroidism. The parathyroid hormone (PTH) secretory reserve is reduced in a significant number of 22q11.2 deletion syndrome patients with normocalcemia. The aim of this study was to investigate hypoparathyroid function using the bicarbonate infusion test for 22q11.2 deletion syndrome with normocalcemia.


METHODS
sodium bicarbonate solution [7% (w/v); 40 ml/m(2) body surface area] was infused for 2 min, and blood samples for the determination of plasma ionized calcium and plasma intact PTH were serially obtained. The test was conducted on five 22q11.2 deletion syndrome patients with normocalcemia.


RESULTS
two patients presented increments of intact PTH levels (peak value - basal value) of 70 pg/ml or higher during the test, whereas the remaining 3 showed PTH level increments of <30 pg/ml. The former 2 patients were diagnosed as having normal parathyroid gland function, and the latter 3 patients as having subclinical hypoparathyroidism.


CONCLUSIONS
the bicarbonate infusion test may be a valuable method for the evaluation of residual parathyroid gland function in patients with 22q11.2 deletion syndrome. Screening of subclinical hypoparathyroidism should be considered in the regular follow-up of patients with 22q11.2 deletion syndrome, even in cases with normocalcemia.
Nagasaki
Keisuke
K
Division of Pediatrics, Department of Homeostatic Regulation and Development, Niigata University Graduate School of Medicine and Dental Sciences, Niigata, Japan. nagasaki@med.niigata-u.ac.jp
Iwasaki
Yasumasa
Y
Ogawa
Yohei
Y
Kikuchi
Toru
T
Uchiyama
Makoto
M
D000293:Adolescent; D000328:Adult; D002118:Calcium / Q000097:blood; D002675:Child, Preschool; D004062:DiGeorge Syndrome / Q000097:blood / Q000503:physiopathology; D003940:Diagnostic Techniques, Endocrine; D042241:Early Diagnosis; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007011:Hypoparathyroidism / Q000175:diagnosis* / Q000209:etiology; D008297:Male; D010280:Parathyroid Glands / Q000503:physiopathology; D010281:Parathyroid Hormone / Q000097:blood; D017693:Sodium Bicarbonate; D013997:Time Factors; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood; D055815:Young Adult
C470125:PTH protein, human; D010281:Parathyroid Hormone; D014807:Vitamin D; D017693:Sodium Bicarbonate; C104450:25-hydroxyvitamin D; D002118:Calcium