Figure 2).

Acute and chronic stressor states with excess catecholamines or aldosteronism, respectively, can lead to plasma-ionized hypocalcemia with secondary hyperparathyroidism (SHPT), in which elevations in plasma parathyroid hormone (PTH) levels seek to restore extracellular Ca²⁺ [Ca²⁺]_o homeostasis via bone resorption, and increase Ca²⁺ absorption and reabsorption from the colon and the kidneys, respectively. Paradoxically, PTH raises intracellular Ca²⁺ [Ca²⁺]_i to induce oxidative stress. [Mg²⁺]_o Extracellular magnesium; mPTP Mitochondrial permeability transition pore. Adapted from reference 119