Adrenocortical Steroids - Vertebrates
The adrenal cortex secretes two types of steroid hormones:
- Glucocorticoids, concerned with regulation of glucose and
- Mineralocorticoids, concerned with salt regulation.
This distinction between glucocorticoids and mineralocorticoids is found in mammals where as nonmammalian vertebrates do not maintain such distinction. In general the action of corticosteroids is adaptive. Salt output or retention is altered in accordance with environmental demands.
In mammals aldosterone, a mineralocorticoid is concerned with electrolytd balance. It is produced in response to adrenoeorticotropic hormone (ACTH) secreted by the pituittary. ACTH itself is released in response to a corticotropin releasing factor (CRF) from the hypothalamus. Glomerulotrophic hormone from the pineal gland is also known to stimulate aldosterone secretion. In nonmammalian vertebrates apart from aldosterone, another mineralocorticoid, cortisol is known to promote NaCl absorption. The mineralocorticoids increase the tubular absorption of sodium and promote the renal excretion of potassium.