HYPERPARATHYROIDISM: HOW MUCH DO CALCIUM AND VITAMIN D MATTER?

Abstract Ref: 
0238

James H Mahon, Oisín Hannigan, Maeve Hennessy, Ronan O’Toole, Paul Claffey,
Nessa Fallon, Georgina Steen, Irina Tomita, MC Casey, JB Walsh, Kevin McCarroll
Bone Health Unit, Medicine for the Elderly Directorate, St. James’s Hospital, Dublin 8, Ireland

Background: Hyperparathyroidism is associated with increased bone turnover and fractures.
We aimed to determine its prevalence in patients attending our osteoporosis clinic,
and investigate relationships between their serum calcium, vitamin D, bone turnover markers,
bone mineral density (BMD), DXA T-scores and fracture history.

Methods: We identified records from 2003–2017, collecting data on parameters above,
and parathyroid imaging. Normal calcium level defined as 2.35–2.50 nmol/litre; normal
vitamin D =/> 50 nmol/litre; normal PTH < 2.65 pg/ml.

Results: 7624 patients; 364 (4.77%) had elevated PTH; 27 with incomplete data
excluded. Of remaining 337, 294 female, 43 male; median age 76, mean T-score spine
−2.6, mean T-score hip −2.4; overall osteoporosis prevalence 68.8%; 19% had prior hip
fracture, 49% vertebral, and 21% Colles.
16 with eGFR < 30 ml/min excluded. Of the remaining 321, 53 (16.5%) hypercalcaemic,
69 (21.5% normocalcaemic and 199 (62%) hypocalcaemic. 182 had low vitamin D,
implying secondary hyperparathyroidism; 139 normal vitamin D, implying primary
hyperparathyroidism.
Of 139 with likely primary hyperparathyroidism, we compared those with normal calcium
level to those with high calcium: No significant differences in BMD spine/hip,
prevalence of osteoporosis or fragility fracture. P1NP – a bone formation marker – was
significantly higher in normocalcaemic group (mean difference 17.483 ng/ml, p = 0.049).

57 patients had parathyroid ultrasound or isotope scans. 22 positive for adenoma; 35
negative. Scans significantly more likely to be positive in patients with high calcium compared
with normal calcium (likelihood ratio 5.671, p = 0.0173, ChiSquare test). 13 positive
scans were in patients with low vitamin D.

Conclusions: Patients with hyperparathyroidism were relatively older, osteoporotic and
had high prevalence of fractures, low serum calcium and vitamin D. Low vitamin D was
a poor negative predictor of adenoma. Although normocalcaemic patients were less likely
to have a radiologically-proven adenoma, they appeared to carry a similar risk of osteoporosis
and fracture as those with high calcium/adenoma.