Primary hyperparathyroidism (PHPT) is a common endocrine condition which disrupts physiologic
calcium regulation. PHPT causes persistent
hypercalcemia via the elevated and constant secretion of
parathyroid hormone. Due to the effects of
parathyroid hormone on target organs such as the bones, kidneys and gastrointestinal tract, untreated PHPT can lead to complications such as decreased bone mineral density,
nephrolithiasis, and chronic
abdominal pain, respectively. Given PHPT's drastic effect on
calcium metabolism, it is likely that the condition also affects other organ systems, such as the inner ear, which rely on
calcium for normal structure and function. Specifically, the saccule and utricle have otoconia made of
calcium carbonate deposited on a
protein framework. We hypothesize that PHPT, the epitome
calcium disorder, can cause otoconia degeneration, one manifestation of which is
benign paroxysmal positional vertigo (BPPV). As a preliminarily test of this hypothesis, we measured the levels of
otolin-1, an inner ear
glycoprotein found in the otoconia
protein framework and a proposed
biomarker for otoconia degeneration in patients with PHPT. We found a positive linear relationship between PTH (
parathyroid hormone) and
otolin-1 levels (R2 = 0.53) and total
calcium and PTH levels (R2 = 0.32). These findings suggest that both PTH and total
calcium levels affect
otolin-1 levels, implying that the
calcium dysregulation caused by PHPT may contribute to the otoconia breakdown and may be associated with inner ear disorders such as BPPV.