Diagnosis of normocalcemic hyperparathyroidism by oral calcium loading test.
We evaluated the oral calcium-loading test (OCLT) in diagnosing normocalcemic primary hyperparathyroidism. Calcium and PTH levels were measured before, 60, 120 and 180 min after oral 1 g of calcium gluconolactate administration in 102 consecutive females with high circulating PTH levels, and 25 controls. Patients were classified as follows: Group A, patients with a parathyroid adenoma identified by two imaging modalities. Sub-Group AO, hyperparathyroid patients [no.=13, mean age 59 yr (SD=10)] evaluated prior to parathyroidectomy. Sub-Group AH, non-operated hypercalcemic patients [no.=29, age 63 yr (SD=11)]. Sub-Group AN, normocalcemic non-operated women [no.=14, age 59 yr (SD=8)]. Group B, normocalcemic individuals [no.=46, age 58 yr (SD=11)] with negative parathyroid imaging. Group C, control patients [no.= 25, age 56 yr (SD=12)]. The concentrations of calcium and PTH overlapped in the normocalcemic groups during the OCLT. Product P, defined as circulating PTH nadir (pg/ml) x peak calcium concentration (mg/dl), better discriminated Sub-Group AN from Group B, AUC=0.98 (95% CI 0.95, 1.00) than did Ratio R, defined as relative PTH decline/relative calcium increment, AUC= 0.86 (95%CI 0.73, 0.99). Assuming normal threshold of Product P and Ratio R at 260 and 17 respectively, the combined parameters diagnose normocalcemic hyperparathyroid patients with 100% sensitivity and 87% specificity.
Hagag
P
P
Endocrine Institute, Assaf Harofeh Medical Center, Zerifin, Israel. phagag@asaf.health.gov.il
Revet-Zak
I
I
Hod
N
N
Horne
T
T
Rapoport
M J
MJ
Weiss
M
M
D000236:Adenoma / Q000097:blood* / Q000175:diagnosis; D000284:Administration, Oral; D000368:Aged; D002118:Calcium / Q000008:administration & dosage / Q000097:blood; D005260:Female; D006801:Humans; D006961:Hyperparathyroidism / Q000097:blood / Q000145:classification / Q000175:diagnosis*; D010281:Parathyroid Hormone / Q000097:blood*; D010282:Parathyroid Neoplasms / Q000097:blood* / Q000175:diagnosis; D011446:Prospective Studies; D012016:Reference Values; D012680:Sensitivity and Specificity
D010281:Parathyroid Hormone; D002118:Calcium