Plasma 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and parathyroid hormone in familial hypocalciuric hypercalcemia and primary hyperparathyroidism.
BACKGROUND
Familial hypocalciuric hypercalcemia (FHH) is a lifelong, benign, inherited condition caused by inactivating mutations in the calcium-sensing receptor (CASR) gene. Both FHH and primary hyperparathyroidism (PHPT) are characterized by elevated P-calcium, normal or elevated plasma-parathyroid hormone (P-PTH), and typically normal renal function. In PHPT, vitamin D metabolism is typically characterized by low plasma levels of 25-hydroxyvitamin D (25OHD), and high plasma levels of 1,25-dihydroxyvitamin D (1,25(OH)(2)D). In FHH, the vitamin D metabolism is not very well known.


OBJECTIVE
To compare and evaluate plasma 25OHD, 1,25(OH)(2)D, and PTH in FHH and PHPT.


METHODS
Cross-sectional study.


METHODS
About 66 FHH patients with mutations in the CASR gene, 147 patients with surgically verified PHPT, and 46 controls matched to FHH patients according to age (+/-5 years), sex, and season. All patients had a P-creatinine <140 micromol/l.


METHODS
We measured P-calcium, P-Ca(2)(+), P-albumin, P-creatinine, P-phosphate, P-magnesium, and P-PTH by standard laboratory methods. P-25OHD and P-1,25(OH)(2)D were measured by RIA or enzyme immunoassay. In FHH, all protein-coding exons in the CASR gene were sequenced and aligned to GenBank reference sequence NM_000388.2.


RESULTS
PHPT patients had higher body mass index (2p<0.01), together with higher P-PTH (2p<0.01) and P-1,25(OH)(2)D (2p<0.01) compared with FHH patients. The groups had similar levels of P-Ca(2)(+) and of P-25OHD. The phenotypic expression of the CASR mutations (as determined by the degree of hypercalcemia) did not influence the levels of P-1,25(OH)(2)D.


CONCLUSIONS
Even though P-calcium and P-25OHD were comparable, P-1,25(OH)(2)D and P-PTH differed between FHH and PHPT.
Christensen
Signe Engkjaer
SE
Department of Endocrinology, Aarhus University Hospital, Aarhus Sygehus, Tage-Hansens gade 2, DK 8000 Arhus C, Denmark. rlg06sec@as.aaa.dk
Nissen
Peter H
PH
Vestergaard
Peter
P
Heickendorff
Lene
L
Rejnmark
Lars
L
Brixen
Kim
K
Mosekilde
Leif
L
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006934:Hypercalcemia / Q000097:blood* / Q000175:diagnosis / Q000235:genetics*; D049950:Hyperparathyroidism, Primary / Q000097:blood* / Q000175:diagnosis / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D044169:Receptors, Calcium-Sensing / Q000235:genetics; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D055815:Young Adult
C095550:CASR protein, human; C470125:PTH protein, human; D010281:Parathyroid Hormone; D044169:Receptors, Calcium-Sensing; D014807:Vitamin D; C097949:1,25-dihydroxyvitamin D; C104450:25-hydroxyvitamin D