Abstract
The serum levels of parathyroid hormone and magnesium depend on each
other in a complex manner. The secretion of parathyroid hormone by
the parathyroid is physiologically controlled by the serum calcium
level, but magnesium can exert similar effects. While low levels
of magnesium stimulate parathyroid hormone secretion, very low serum
concentrations induce a paradoxical block. This block leads to clinically
relevant hypocalcemia in severely hypomagnesiemic patients. The mechanism
of this effect has recently been traced to an activation of the alpha-subunits
of heterotrimeric G-proteins. This activation mimicks activation
of the calcium sensing receptor and thus causes inhibition of parathyroid
hormone secretion. In addition to the effects of magnesium on parathyroid
hormone secretion, parathyroid hormone in turn regulates magnesium
homeostasis by modulating renal magnesium reabsorption. The distal
convoluted tubule is of crucial importance for parathyroid hormone-regulated
magnesium homeostasis.
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