Association between High Levels of Parathyroid Hormone and Frailty: The Nepean Osteoporosis and Frailty (NOF) Study.

BACKGROUND: Frailty is associated with poor outcomes hence identification of risks factors is pivotal. Since the independent role of parathyroid hormone (PTH) in frailty remains unexplored, we aimed to determine this in a population of older individuals with a history of falling.

DESIGN: Cross-sectional study.

SETTING: Falls and Fracture Clinic, Nepean Hospital (Penrith, Australia).

PARTICIPANTS: 692 subjects (mean age=79, 65% women) assessed between 2009-2015.

MEASUREMENTS: Assessment included clinical examination, mood, nutrition, grip strength, gait velocity, bone densitometry and posturography. Chemistry included serum PTH, calcium, vitamin D (25(OH)D3), creatinine and albumin. Normocalcemic subjects were divided into 4 groups: (1) Normal: 25(OH)D3 >50nmol/L and PTH between 1.6-6.8pmol/L; (2) PTH responsive: low 25(OH)D3 (<50nmol/L) and high PTH (>6.8pmol/L); (3) PTH unresponsive: low 25(OH)D3 and normal PTH; (4) Hyper PTH (>6.8pmol/L) with normal 25(OH)D3. Frailty was defined using Fried's criteria. Difference between the groups was assessed using one-way ANOVA and X2 analysis. Multinomial logistic regression evaluated the association between the groups and the number of Fried's criteria adjusted for age, BMI, renal function, 25(OH)D3 levels, and albumin.

RESULTS: 22.6% subjects had high PTH levels (>6.8pmol/L). All subjects in the high PTH groups had significantly lower grip strength, gait velocity, limits of stability, and higher BMI. The PTH responsive group had a higher risk of pre-frailty (β=3.8, 95% CI = 3.42 - 5.22, p≷ 0.01) and frailty (β=8.26, 95% CI = 2.8-16.1, p<0.01). The risk of frailty was also higher in the Hyper PTH group (β=2.3, 95% CI = 1.74-4.32, p<0.01).

CONCLUSION: We have reported an independent association of high PTH levels with high number of falls and with the clinical components of physical frailty in community dwelling older persons. Our results suggest a possible role of PTH in frailty that deserves further exploration.