The vitamin d receptor in thyroid development and function.
OBJECTIVE
Vitamin D is known to modulate thyroid neoplastic and autoimmune disease. We investigated the role of the vitamin D receptor (VDR) in normal thyroid development and function (thyrocytes and C cells).


METHODS
The thyroid phenotype of VDR knockout mice was studied in comparison to wild-type controls. The mice were fed a normal diet or a calcium-rich diet to circumvent effects induced by hypocalcemia.


RESULTS
Thyroid morphology was unaltered in VDR knockout mice. Also, expression of different parameters of thyrocyte function was comparable (immunohistochemistry). C cell physiology was, however, affected in the absence of the VDR, resulting in increased thyroidal calcitonin expression (immunohistochemistry), paralleled by increased serum calcitonin levels, but only in normocalcemic mice. To study a possible effect of vitamin D status on basal calcitonin levels in humans, serum calcitonin concentrations were compared between vitamin D-deficient and -sufficient patients (serum 25-OH vitamin D3 ≤10 and ≥40 ng/ml, respectively), but no difference was observed.


CONCLUSIONS
In mice, the VDR is redundant for normal thyrocyte function, but not for C cell function, where it mediates the negative control of calcitonin by 1,25-dihydroxyvitamin D3. In patients, vitamin D status does not affect basal serum calcitonin levels. A study in healthy individuals is needed to confirm these findings.
Clinical and Experimental Endocrinology, Katholieke Universiteit Leuven, Leuven, Belgium.
Isabelle
I
Clinckspoor
Pôle de Morphologie, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Leuven, Belgium.
Anne-Catherine
AC
Gérard
IRIBHM, Université Libre de Bruxelles, Brussels, Leuven, Belgium.
Jacqueline
J
Van Sande
Pôle de Morphologie, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Leuven, Belgium.
Marie-Christine
MC
Many
Clinical and Experimental Endocrinology, Katholieke Universiteit Leuven, Leuven, Belgium.
Lieve
L
Verlinden
Clinical and Experimental Endocrinology, Katholieke Universiteit Leuven, Leuven, Belgium.
Roger
R
Bouillon
Clinical and Experimental Endocrinology, Katholieke Universiteit Leuven, Leuven, Belgium.
Geert
G
Carmeliet
Clinical and Experimental Endocrinology, Katholieke Universiteit Leuven, Leuven, Belgium ; Department of Endocrinology, University Hospitals Leuven, Leuven, Belgium.
Chantal
C
Mathieu
Clinical and Experimental Endocrinology, Katholieke Universiteit Leuven, Leuven, Belgium.
Annemieke
A
Verstuyf
Clinical and Experimental Endocrinology, Katholieke Universiteit Leuven, Leuven, Belgium ; Department of Endocrinology, University Hospitals Leuven, Leuven, Belgium.
Brigitte
B
Decallonne
Calcitonin; Calcium; Thyroid; Vitamin D; Vitamin D receptor