The following statements regarding Vitamin D3 are true except:
Chronic injection of large doses can result in hypervitaminosis.
It is useful in postmenopausal osteoporosis.
Its active metabolite is calcitriol.
It is ineffective in the treatment of vitamin D resistant rickets.
The active metabolite of vitamin D is calcitriol. Hypervitaminosis can result due to ingestion of large doses for a prolonged time. Vitamin D therapy can suppress parathyroid function and reduce bone turnover in osteoporosis. It may also improve intestinal absorption of calcium. Vitamin D along with inorganic phosphates provides clinical improvement in patients with vitamin D-resistant rickets, which is characterized by deranged calcium and phosphate metabolism despite normal calcitriol levels.