What Is PTH 1-34? Benefits, Research & Safety

Parathyroid hormone was identified in the early 20th century as the factor controlling calcium homeostasis. For decades, it was primarily associated with hypercalcemia and bone loss in hyperparathyroidism. The surprising observation that intermittent PTH administration could increase bone mass dates to the 1970s and 1980s. Researchers found that while continuous PTH caused bone resorption, pulsed/intermittent exposure stimulated bone formation—a phenomenon sometimes called the "anabolic window." Studies in osteoporotic patients in the 1990s demonstrated that daily PTH injections increased bone density and reduced fractures. The 1-34 fragment was found to have full biological activity and was easier to produce recombinantly. The pivotal Fracture Prevention Trial demonstrated significant reductions in vertebral and non-vertebral fractures with teriparatide. The FDA approved teriparatide (Forteo) in 2002 for postmenopausal osteoporosis. The rat osteosarcoma signal observed in preclinical studies led to a boxed warning and the 2-year treatment limitation, though no increase in osteosarcoma has been observed in humans even with long-term surveillance. Subsequent developments include abaloparatide (PTHrP analogue) and combination/sequential therapy studies optimising the anabolic-to-antiresorptive transition.