Extremely elevated serum alkaline phosphatase level upon treatment with teriparatide: a case report

Teriparatide is a homolog of human parathyroid hormone (1-34), which is approved for the treatment of postmenopausal and glucocorticoid-induced osteoporosis. Several minor and transient side effects have been reported for teriparatide. However, controversial findings showed an increased risk of more significant adverse effects, including osteosarcoma in humans, although this finding has been demonstrated primarily in murine models.

We present a case of a 22-year-old Persian man with a previous history of systemic lupus erythematosus and glucocorticoid-induced osteoporosis. He had a previous history of joint hypermobility, idiopathic kyphoscoliosis, mitral valve prolapse, and bilateral congenital inguinal hernia, which were probably compatible with an inherited connective tissue disease. He was treated with teriparatide for 7 months because of glucocorticoid-induced osteoporosis. He was referred with a complaint of generalized bone pain and an extremely elevated serum alkaline phosphatase concentration of 6480 U/L (normal range, 80-306). A whole-body bone scan revealed a diffuse increased osseous uptake. Furthermore, the patient's systemic lupus erythematosus was clinically inactive on the basis of laboratory findings during this period. The medication was discontinued, and the patient's serum alkaline phosphatase level began to decline.

To the best of our knowledge, this is the first case of an osteoblast hyperactivation state observed during treatment with teriparatide. It appears that the osteoblastogenic effect of teriparatide might induce this condition and, most likely, osteosarcoma in certain populations. However, the potential influence of the patient's young age, systemic lupus erythematosus, underlying inherited connective tissue disease, and medication use cannot be ignored. The potential risk factors of this side effect shall be studied in specific subpopulations of patients with osteoporosis in future studies.