Vitamin D3 intoxication in naked mole-rats (Heterocephalus glaber) leads to hypercalcaemia and increased calcium deposition in teeth with evidence of abnormal skin calcification.

Naked mole-rats have no access to obvious sources of vitamin D and therefore have an impoverished vitamin D status. In an investigation into the effects of vitamin D supplementation, inadvertently supraphysiological doses of 130,000 times the normal dose of vitamin D were administered. Within 5 days animals appeared lethargic, with reduced food intake. All but one of the seven animals were killed and blood was collected. Plasma vitamin D metabolites 25(OH)D and 1,25(OH)2D and calcium were determined. Both vitamin D metabolite concentrations exceeded the upper limits of sensitivity of the assays (> 100 ng/ml 25(OH)D and > 210 pg/ml 1,25(OH)2D). Active calcium uptake in the intestine was evident along with concomitant increases in calcium concentration in plasma, bone, and teeth. The remaining animal survived, but showed scab-like formations in the skin around the lower jaw and along the nipple line. X-ray analyses revealed calcium deposition in these cornified regions, although there was no evidence of metastatic calcification in other tissues. Deposition of excess calcium in skin that is regularly sloughed off and in teeth that are continuously worn down and replaced may reduce the vitamin D-induced hypercalcaemia and thus alleviate the effects of vitamin D intoxication.