[Sensitivity of bone to parathyroid hormone in type I pseudohypoparathyroidism. 6 cases]

The sensitivity of bone to parathormone in pseudoparathyroidism is not well known. Six patients with Type I pseudohypoparathyroidism (4 with Albright's osteodystrophy) had increased alkaline phosphatase levels (5 patients) and radiological signs of periosteal resorption in the hand in one case. All patients had histological signs of increased surfaces of resorption and periosteocytic lacunae, increased osteoid surfaces and relative osteoid volume with no change of the index of osteoid thickness. These changes are identical to those observed in hyperparathyroidism which leads on to the discussion of the role of the increased parathormone secretion induced by the lack of calcium on the remodeling of bone. Our six cases show that there is no bone resistance to parathormone. The diversity of bone changes in hyperparathyroidism, similar to that of primary hyperparathyroidism, is without doubt dependent on the degree of renal insensitivity to PTH through the inactivation of vitamin D.