Global skeletal uptake of 99mTc-methylene diphosphonate (GSU) in patients affected by endocrine diseases: Comparison with biochemical markers of bone turnover

This study aimed to clinically validate the global skeletal uptake (GSU) of ^99mTc-methylene diphosphonate (^99mTc-MDP), and to compare it with a marker of bone formation (i.e. serum osteocalcin or OC) and an index of bone resorption (i.e. urinary deoxypyridinoline or U-DPD) in different endocrine disorders affecting the skeleton. We studied 29 female patients with thyrotoxicosis (TT), 27 with primary hyperparathyroidism (PHPT), 16 with acromegaly (AC), 15 with Cushing's syndrome (CS), and altogether 110 healthy women matched for age, BMI and menstrual status. In all subjects total body digital scan images (TBDS) were acquired at 5 min and at 4 h after the administration of ^99mTc-MDP; the whole body retention (WBR) of the tracer was measured by counting two identical sets of rectangular ROIs, and GSU was subsequently calculated by drawing an irregular ROI on 4 h TBDS images. Serum OC was assessed by IRMA and urinary DPD by fluorometric detection after reverse phase high pressure chromatography. In TT patients GSU (40.0 ± 5.1 vs 36.5 ± 4.8%), OC (19.1 ± 11.8 vs 7.1 ± 2.9 μg/l) and U-DPD (62.4 ± 42.7 vs 19.5 ± 5.3 pmol/pmol) were significantly (p