Evaluation of Parathyroid Gland Function Using Sodium Bicarbonate Infusion Test for 22q11.2 Deletion Syndrome

Abstract

Background/Aims: 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/m² 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. Conclusion: 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.

Delayed diagnosis of 22q11 deletion syndrome due to late onset hypocalcemia in a 11-year-old girl with imperforated anus

“…A recent study including 138 adults with 22q11DS reported 80% of patients have a lifetime history of hypocalcaemia8). The spectrum of parathyroid gland function in 22q11DS ranges from severe neonatal hypocalcemia to latent hypoparathyroidism28).…”

“…The spectrum of parathyroid gland function in 22q11DS ranges from severe neonatal hypocalcemia to latent hypoparathyroidism28). The PTH secretory reserve is inadequate compared with normal population in patients with latent hypoparathyroidism3), and it becomes insufficient that can lead to evident hypocalcemia when calcium requirement increases such as during adolescence, pregnancy, surgery, infection, or any physiologic stresses29).…”

“…A provocation test using sodium bicarbonate infusion was reported to be able to evaluate residual parathyroid function in normocalcemic patients with 22q11DS8). Hypocalcemia may also be worsened by carbonated beverages such as colas9).…”

Two cases of 22q11.2 deletion syndrome with decreased serum calcium during recovery following thyrotoxicosis

“…The most common chromosomal microdeletion syndrome, 22q11.2 deletion syndrome (22qDS), mainly manifests as hypoparathyroidism, which varies from overt to subclinical presentation, and is often asymptomatic 1 . Parathyroid hormone (PTH) reserve, the response of PTH to the sodium bicarbonate infusion test, is reduced in many patients with 22qDS having normocalcemia 2 …”

“…1 Parathyroid hormone (PTH) reserve, the response of PTH to the sodium bicarbonate infusion test, is reduced in many patients with 22qDS having normocalcemia. 2 22qDS is associated with high-autoimmune thyroid disease incidence. 3 Hypercalcemia due to thyrotoxicosis is rarely reported, which means that thyroid hormones affect calcium (Ca) metabolism.…”