HYPOMAGNESEMIA WITH INCREASED METABOLISM OF PARATHYROID-HORMONE AND REDUCED RESPONSIVENESS TO CALCITROPIC HORMONES
HYPOMAGNESEMIA WITH INCREASED METABOLISM OF PARATHYROID-HORMONE AND REDUCED RESPONSIVENESS TO CALCITROPIC HORMONES
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DOI：
10.2169/internalmedicine.31.820
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发表时间：
1992-06-01
影响因子：
1.2
通讯作者：
OGATA, E
中科院分区：
文献类型：
--
作者：
MORI, S;HARADA, S;OGATA, E
本文报告一例慢性酒精中毒引起的严重低镁血症患者，其甲状旁腺激素（PTH-M）中段的放射免疫测定结果与血清全段PTH（PTH-全段）的免疫放射测定结果之间存在分离，反复出现明显的低钙血症。血清甲状旁腺素-M中度升高，而血清甲状旁腺素-完整的是在正常范围内的低时，她的血清镁（Mg）浓度显着降低。血清骨钙素浓度也明显降低。补充镁导致血清PTH水平急剧增加，两种PTH免疫测定之间的解离迅速消失。在血清PTH和1，25（OH）2D水平达到峰值后不久，血清骨钙素开始升高，并随着血清Ca浓度的正常化而升高至超正常水平。Mg被认为是钙（Ca）的模拟物/拮抗剂，并且显示高细胞外Ca导致分泌抑制，同时刺激PTH的降解。因此，这些观察结果是一致的假设，即镁缺乏导致甲状旁腺素的代谢增加和减少分泌的生物活性完整的甲状旁腺素通过增加甲状旁腺细胞的敏感性钙。此外，低钙血症消失的同时血清骨钙素从检测不到的水平显着增加的事实表明，难治性的骨钙激素是存在的，这在低镁血症下的低钙血症的发展中起着重要作用，血清骨钙素可以是一个很好的标志物评估骨钙激素在这些患者中的反应。
A patient with severe hypomagnesemia due to chronic alcoholism is presented who repeatedly exhibited marked hypocalcemia with a dissociation between radioimmunoassay findings for mid region of parathyroid hormone (PTH-M) and immunoradiometric assay findings of serum intact PTH (PTH-intact). Serum PTH-M was moderately elevated whereas serum PTH-intact was in a low normal range every time when her serum magnesium (Mg) concentration was markedly reduced. There was also a marked reduction in serum osteocalcin concentration. Supplementation of Mg resulted in a sharp increase in serum PTH level with a rapid disappearance of the dissociation between the two immunoassays of PTH. Shortly after serum PTH and 1,25(OH)2D levels reached their peak, serum osteocalcin started to increase, and was elevated into a supranormal level with normalization of serum Ca concentration. Mg is thought to act as a mimic/antagonist of calcium (Ca), and high extracellular Ca is shown to cause an inhibition of secretion with a stimulation of degradation of PTH. Thus, these observations are consistent with the hypothesis that Mg deficiency causes an increase in the metabolism of PTH and a reduction in the secretion of bioactive intact PTH by increasing the sensitivity of parathyoid cells to Ca. In addition, the fact that hypocalcemia disappeared concomitant with a marked increase of serum osteocalcin from undetectable levels suggest that refractoriness of bone to calcitropic hormones is present which plays a significant role in the development of hypocalcemia under hypomagnesemia, and that serum osteocalcin can be a good marker for the assessment of the responsiveness of bone to calcitropic hormones in these patients.