In patients with markedly low bone density, prevalent fractures, or high doses of steroids I usually also check a PTH and 25-hydroxyvitamin D level . In less severe cases I will just check these if the serum calcium or alkaline phosphatase is abnormal. Xrays of the spine are especially important in patients taking long-term corticosteroids, because sometimes the fractures are not clinically obvious, and if they are present the patient will need maximal therapy. The physiology of corticosteroid-induced osteoporosis is different than postmenopausal osteoporosis, so treatment cannot be expected to have the same results. For example, anti-resorptive therapy does not result in the same degree of increase in bone mass as in postmenopausal osteoporosis.
Greater amounts are unlikely to be beneficial.
The use of vitamin D in corticosteroid-treated osteoporosis is debated, and there is still not enough data to make strong recommendations. The most recent studies do not show a difference in bone density with active vitamin D metabolites or high doses of ergocalciferol. Anti-resorptive therapy can prevent some of the bone loss. These studies really don't have enough power to measure fracture prevention, and the only beneficial effect on fractures has been seen in postmenopausal women not taking estrogen. These therapies should not be used in patients with low serum calcium, and adequate dietary intake should be assured before they are started.