ORAL ISOTRETINOIN THERAPY IN SEVERE ACNE INDUCES TRANSIENT SUPPRESSION OF BIOCHEMICAL MARKERS OF BONE TURNOVER AND CALCIUM HOMEOSTASIS

Although dietary vitamin A is required for normal growth and developme nt, long-term or high-dose administration of vitamin A derivatives (re tinoids) may produce a variety of skeletal side-effects in man. In thi s study we investigated the early effects of oral isotretinoin therapy on bone turnover and calcium homeostasis in eleven consecutive patien ts with nodulocystic acne, The effects on bone metabolism were correla ted to radiological and bone mineral density measurements following dr ug therapy for six months. Markers of bone turnover, i.e. serum osteoc alcin, the carboxyterminal propeptide of type I collagen, bone specifi c alkaline phosphatase, the carboxyterminal telopeptide of type I coll agen, and urine levels of calcium and hydroxyproline decreased signifi cantly within five days of treatment (p < 0.05), There was also a stat istically significant decrease in serum calcium, with a minimum on day five, and a marked increase in serum parathyroid hormone (p<0.05). Wi th continued treatment, however, the abnormal levels of these markers returned to baseline values within 14 days. No significant roentgenolo gical changes or effects on bone mineral density were found in respons e to the drug. The observed inhibitory effects of isotretinoin on bone turnover, despite elevated parathyroid hormone levels, indicates that the drug exerts a direct effect on bone tissue.