nabolic or catabolic?—Evolution of the 20th century understanding of parathyroid hormone's therapeutic actions on the skeleton

The first successful parathyroidectomy in 1925 for hyperparathyroidism triggered the widespread conviction for half a century that parathyroid hormone (PTH) was invariably catabolic for the skeleton. This was despite early work with impure PTH preparations that had usually showed in young rats an anabolic skeletal response. While this in vivo work was mostly forgotten over the next three decades, Edith Bülbring, one of the first investigators of in vivo PTH administration, pointed out the folly of not formally testing the hypothesis that calcitonin rather than parathyroid hormone was responsible for the apparently anabolic skeletal effects of impure PTH administration. This chapter traces the subsequent three decades of investigation leading to the phase 3 Clinical Trial of teriparatide that resulted in its licensing for the treatment of osteoporosis.