Parathyroid hormone response to severe vitamin D deficiency is sex associated: an observational study of 571 hip fracture inpatients.
OBJECTIVE
To investigate the association between sex and parathyroid hormone response to severe vitamin D deficiency after hip fracture.


METHODS
Cross-sectional study.


METHODS
Rehabilitation hospital in Italy.


METHODS
571 consecutive inpatients with hip fracture and severe vitamin D deficiency (serum 25-hydroxyvitamin D < 12ng/ml), without hypercalcemia or estimated glomerular filtration rate (GFR) < 15ml/min.


METHODS
In each patient we assessed PTH (by two-site chemiluminescent enzyme-labelled immunometric assay), 25-hydroxyvitamin D (by immunoenzymatic assay), albumin-adjusted total calcium, phosphate, magnesium, and creatinine 21.3 ± 6.1 (mean ± SD) days after fracture occurrence. Functional level was assessed using the Barthel index. PTH response to vitamin D deficiency was classified as either secondary hyperparathyroidism (serum PTH >75pg/ml) or functional hypoparathyroidism, i.e., inappropriate normal levels of PTH (≤75pg/ml).


RESULTS
Among the 571 patients, 336 (59%) had functional hypoparathyroidism, whereas 235 (41%) had secondary hyperparathyroidism. PTH status was significantly different between sexes (p=0.003): we found functional hypoparathyroidism in 61% of women and 43% of men (secondary hyperparathyroidism in 39% of women and 57% of men). The significance of the between-sex difference was maintained after adjustment for age, estimated GFR, phosphate, albumin-adjusted total calcium, albumin, Barthel index scores, 25-hydroxyvitamin D, and hip fracture type (either cervical or trochanteric). The adjusted odds ratio was 1.85 (95%CI from 1.09 to 3.13; p=0.023).


CONCLUSIONS
Data shows that PTH response to vitamin D deficiency was sex-associated following a fracture of the hip. The higher prevalence of secondary hyperparathyroidism may play a role in the known prognostic disadvantage found in hip-fracture men.
Osteoporosis Research Center, Division of Physical Medicine and Rehabilitation, Presidio Sanitario San Camillo, Torino, Italy. marco.di.monaco@alice.it
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Di Monaco
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Castiglioni
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Vallero
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Di Monaco
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Tappero
D000368:Aged; D000369:Aged, 80 and over; D003404:Creatinine / Q000097:blood; D003430:Cross-Sectional Studies; D005260:Female; D015577:Geriatric Assessment; D006620:Hip Fractures / Q000097:blood / Q000209:etiology*; D006801:Humans; D006962:Hyperparathyroidism, Secondary / Q000453:epidemiology / Q000209:etiology*; D007011:Hypoparathyroidism / Q000453:epidemiology / Q000209:etiology*; D008297:Male; D019370:Observation; D016017:Odds Ratio; D010281:Parathyroid Hormone / Q000097:blood*; D015995:Prevalence; D036301:Qualitative Research; D012720:Severity of Illness Index; D012737:Sex Factors; D014131:Trace Elements / Q000097:blood; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications*
D010281:Parathyroid Hormone; D014131:Trace Elements; D014807:Vitamin D; C104450:25-hydroxyvitamin D; D003404:Creatinine