title: Effects of calcium supplementation and sunlight exposure on growing beagle dogs.
abstract: Nine 7-week-old Beagle dogs were given 2.3 g of dietary calcium supplementation once a day and were exposed to sunlight to permit endogenous vitamin D formation. After 70 days, the serum calcium and phosphorus concentrations, thyroid morphometry, and bone density and composition were compared with those values in a similar group of 10 dogs not given calcium supplementation and maintained in restricted, artificial light. Lower serum calcium and phosphorus concentrations in the supplement-fed dogs may be attributed to hypercalcitonism, which was assumed to be present because of increased proportions of C cells and decreased proportions of thyroid follicles. They also had significantly more trabecular bone of a lower specific gravity containing more water and less combustible matter. The findings indicate that the high dietary calcium intake and sunlight exposure induced C-cell hyperplasia during a relatively short period of 70 days. It is possible that Beagles maintained through maturity on a diet high in calcium concentration and in outdoor runs may develop chronic C-cell hyperplasia. The possible contribution of high calcium intake and chronic C-cell hyperplasia to reduced thyroid function and skeletal changes is not yet clear.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D004285:Dogs / Q000254:growth & development* / Q000378:metabolism / Q000502:physiology; D005260:Female; D008297:Male; D010758:Phosphorus / Q000378:metabolism; D013472:Sunlight; D013961:Thyroid Gland / Q000166:cytology / Q000378:metabolism; D014807:Vitamin D / Q000378:metabolism
chemical_list: D014807:Vitamin D; D010758:Phosphorus; D002118:Calcium