Michiko Yamamoto

Ossification of the paravertebral ligaments: A frequent complication of hypoparathyroidism

Various forms of paravertebral ligamentous ossification (PVLO) were detected radiologically in 9 (53%) of 17 consecutive patients with hypoparathyroidism. A significant correlation was found between the period during which the patient was untreated and the incidence of ossification. Serum levels of calcium, phosphate, and their ionic product appeared not to influence the incidence. All the patients with PVLO exhibited evidence of ectopic calcification. The fact that ectopic ossification, which is histologically distinct from ectopic calcification, is frequently associated with hypoparathyroidism suggests that similar pathogenetic mechanisms are responsible for the development of these two conditions. The high incidence of PVLO in hypoparathyroid patients in this study may explain some of the neurologic findings in hypoparathyroidism that have been hard to explain simply on the basis of altered neuromuscular excitability.

Human PTH(1–34) infusion test in differential diagnosis of various types of hypoparathyroidism: an attempt to establish a standard clinical test

To introduce a simple procedure and reliable diagnostic criteria for parathyroid hormone (PTH) infusion test, 128 patients with either pseudo- (PsH) or idiopathic hypoparathyroidism (IdH) and 25 normocalcemic controls were studied. Incremental responses of urinary cyclic AMP and phosphate to 20 micrograms (67 U) or 30 micrograms (100 U) of human PTH(1-34) were assessed by using simple parameters of urinary excretion rates of the two substances. The results are summarized as follows. (1) PTH dose-cyclic AMP response relation suggests that 100 U of PTH is more appropriate than 67 U as a standard test dose for adults. (2) By presenting the magnitude of cyclic AMP response as either net increase or fold increase during 1 h after 100 U of PTH infusion, we can differentiate PsH type I from others without overlap. (3) Differentiation between PsH and IdH or normocalcemic subjects by phosphaturic response is less clearcut than that made by cyclic AMP response whatever indices and criteria are used. Thus it seems difficult to diagnose PsH type II merely based on the discrepancy between cyclic AMP and phosphaturic responses to exogenous PTH. (4) The test results are essentially similar in the examinations performed before and during vitamin D therapy. However, when the magnitude of phosphaturic response is expressed as net increase during 2 h after PTH, it tends to be enhanced after vitamin D therapy in patients with PsH compared to the response before therapy.