Urinary excretion of hydroxyprolines in man under the influence of cold.

Urinary hydroxyproline excretion was studied in human subjects exposed to cold stress and was related to urine flow and tubular reabsorption of calcium and phosphate. The results indicate the occurrence of a calcium release from the bones, which does not seem to be caused by changed activity or immobilization. The cold-induced changes--calcium excretion, dehydration, and demineralization - are the same as those reported under space-flight conditions. Furthermore, it has also been possible to induce a similar response with psychological stress agents. These findings, together with recent observations on renal stone formation and hyperparathyrodism, indicate that different types of stress might have a direct influence on calcium homeostasis, possibly mediated by the adrenergic nervous system.