Four hormones regulate urine concentration and blood sodium levels in humans.
1. Antidiuretic hormone (ADH): Antidiuretic hormone is produced from the pituitary gland. It is also called vasopressin. When the water level in the blood decreases, more ADH is secreted. It increases the water absorption capacity of the renal tubules. As a result, the volume of urine decreases and the concentration of urine increases. The quantity and number of urine released from the body decreases. On the other hand, when the water level in the blood increases, the amount of ADH secretion decreases. This reduces the water absorption capacity of the renal tubules. As a result, urine volume increases and urine concentration decreases. The quantity and number of urine released from the body increases. Human diabetes insipidus occurs when the ADH production of the pituitary gland decreases.
2. Aldosterone hormone: Aldosterone hormone is produced from the cortex of the adrenal gland. It increases the ion and water reabsorption capacity of the kidney. Regulates renal sodium conservation, water retention and increased blood pressure.
3. Atrial natriuretic hormone (ANH): Atrial natriuretic hormone is secreted from the cells of the wall of the atrium of the heart. It increases renal sodium excretion and lowers blood pressure and blood volume. When excess blood flows into the atria, the heart wall expands. As a result, ANH is secreted from the heart wall. ANH dilates the afferent arterioles and increases the glomerular filtration rate. The collecting ducts of the nephron block sodium reabsorption. Renin inhibits angiotensin secretion.
4. Angiotensin-II: Angiotensin-II is an active peptide hormone. Angiotensin-I is secreted inactively from the liver. Inactive Angiotensin-I is then converted to active Angiotensin-II. It increases aldosterone hormone synthesis and secretion. Increases secretion of pituitary gland. Causes constriction of blood vessels and increases blood pressure. Stimulates sodium reabsorption in the proximal convoluted tubule.