endocrinology

Warm hormonal responses

The acclimatization process - thanks to which the human body improves its thermodispersive effectiveness and efficiency over 7-10 days - also includes hormonal adaptations.

These endocrine responses are intended to preserve body hydration, volume (circulating blood volume) and blood pressure, which are put to the test by sweating.

Sweat is in fact a hypotonic liquid (composed mainly of water, with minimal concentrations of electrolytes, mainly sodium, chlorine, potassium and magnesium); therefore, hyper-perspiration causes a greater loss of liquids than mineral salts. The result is an increase in the relative concentration of salts, which leads to increases in the osmotic pressure of interstitial fluids, with a negative effect on the volume of circulating blood.

Volume reduction stimulates the neurohypophysis to produce the antidiuretic hormone (ADH), which acts on the kidney level increasing the reabsorption of water; in this way less dilute urine (with a higher concentration of mineral salts) is eliminated.

Since sodium is the main mineral lost through perspiration, aldosterone secretion also increases during acclimatization, which in the kidney stimulates sodium reabsorption, reducing urinary losses.

As for the short-term endocrine responses, we have seen that exposure to the high temperatures typical of a sauna is accompanied by an important increase in the secretion of ACTH, cortisol, adrenaline and noradrenaline, induced by thermal stress