Surgery for hyperparathyroidism: does morphology or function matter most?

BACKGROUND: With minimally invasive parathyroidectomy (MIP) not all enlarged parathyroid glands are necessarily removed, and intraoperative measurement of parathyroid hormone levels (IO-PTH) does not necessarily predict multiple enlarged glands. The aim of this study was to compare morphology with function, using Ca(2+)-regulated PTH secretion.
METHODS: PTH secretion was determined by perifusion: (1) cells from 12 normal parathyroids were compared with 14 parathyroid adenomas; (2) functional characteristics (PTH secretion, sestamibi uptake, IO-PTH decrease) were correlated with morphologic characteristics; (3) PTH secretion as a predictor of IO-PTH decrease was determined in 7 patients with 2 enlarged parathyroids.
RESULTS: (1) There were significant differences between normal and pathological parathyroid cells consistent with reduced sensitivity to Ca(2+). Maximum secretion rates for normal and adenomatous cells were, respectively, 3.9 +/- 0.4 fg min(-1) cell(-1) and 2.0 +/- 0.4 fg min(-1) cell(-1) (P = .002) and minimum secretion rates, 0.7 +/- 0.1 fg min(-1) cell(-1) and 0.4 +/- 0.1 fg min(-1) cell(-1) (P = .008). However, the IC(50) value for Ca(2+) was elevated in adenomatous cells indicating an apparent loss of extracellular Ca(2+) sensitivity being 1.1 +/- 0.02 mmol/L for normal and 1.2 +/- 0.02 mmol/L for adenomatous cells (P = .02). (2) There was no overall correlation between PTH secretion and gland morphology. (3) In 5 of 7 cases, PTH secretion correctly predicted the decrease in IO-PTH.
CONCLUSION: Parathyroid adenomas generally exhibit abnormal PTH secretory function; however, enlarged parathyroid glands that do not contribute to the biochemical changes of hyperparathyroidism do exist, and, in these cases, cellular secretory function is a useful predictor of IO-PTH dynamics.