Plasma 1,25-dihydroxyvitamin D levels in primary hyperparathyroidism depend on sex, body mass index, plasma phosphate and renal function.
BACKGROUND
Primary hyperparathyroidism (PHPT) is characterized by elevated plasma levels of PTH and calcium with reduced plasma phosphate. Physiologically, renal 1alpha,25-dihydroxyvitamin D [1,25(OH)(2)D] production is stimulated by PTH and phosphate deprivation, and inhibited by 1,25(OH)(2)D itself and calcium.


OBJECTIVE
To investigate relations between circulating levels of 1,25(OH)(2)D, 25-dihydroxyvitamin D (25OHD), PTH, calcium, phosphate, renal function and skeletal complications in patients with PHPT.


METHODS
Cross-sectional study.


METHODS
Two hundred and fifty-two consecutive hypercalcaemic Caucasian patients aged 24-91 (median 65.9) years (85.3% females) with PHPT.


RESULTS
In patients with PHPT, plasma 1,25(OH)(2)D was increased by 27%[107 (9-250) pmol/l, median (range)] compared to controls [84 (18-172) pmol/l, P < 0.001]. In univariate models, plasma 1,25(OH)(2)D depended inversely on age (r = -0.23, P < 0.001) and plasma phosphate (r = -0.23, P < 0.001) and positively on plasma calcium (r = 0.14, P < 0.05), plasma 25OHD (r = 0,15, P < 0.05) and creatinine clearance rate (r = 0.32, P < 0.001). In the final multiple regression model, plasma 1,25(OH)(2)D depended positively on renal function (r(p) = 0.43, P < 0.001) and female sex (r(p) = 0.15, P < 0.05) but inversely on body mass index (BMI; r(p) = -0.23, P < 0.005) and plasma phosphate (r(p) = -0.18, P < 0.05). Plasma 1,25(OH)(2)D correlated positively with renal calcium excretion and inversely with lumbar spine bone mineral density (BMD) but was not associated with risk of fractures or renal stones.


CONCLUSIONS
Patients with PHPT have elevated plasma 1,25(OH)(2)D levels but, to a large extent, individual values overlap controls. The increase in plasma 1,25(OH)(2)D depends on renal function, hypophosphataemia and the female sex and is attenuated by high BMI. High plasma 1,25(OH)(2)D is associated with higher plasma calcium levels.
Moosgaard
B
B
Department of Endocrinology and Metabolism C, Aarhus University Hospital, Aarhus C, Denmark. bmoos@as.aaa.dk
Vestergaard
P
P
Heickendorff
L
L
Mosekilde
L
L
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D015519:Bone Density; D002112:Calcifediol / Q000097:blood; D002117:Calcitriol / Q000097:blood*; D002118:Calcium / Q000097:blood / Q000652:urine; D003404:Creatinine / Q000097:blood / Q000652:urine; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D049950:Hyperparathyroidism, Primary / Q000097:blood* / Q000503:physiopathology; D007668:Kidney / Q000503:physiopathology*; D007677:Kidney Function Tests; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D010710:Phosphates / Q000097:blood*; D011446:Prospective Studies; D012044:Regression Analysis; D012737:Sex Factors
D010710:Phosphates; D003404:Creatinine; D002117:Calcitriol; D002112:Calcifediol; D002118:Calcium