Question

List the hormones secreted by kidney.

Answer 1

The kidneys secrete 3 different types of hormones; erythropoietin, renin and calcitriol (1,25- dihydroxycholecalciferol).

• Erythropoietin and renin are peptide hormones secreted by the juxtaglomerular cells of the kidney
• Calcitriol is a steroid hormone synthesized by the cells of the proximal tubules of the nephrons.

Erythropoietin

• Its production is stimulated by hypoxia (insufficient oxygen supply to the tissues)
• It stimulates the formation of RBC from the haematopoietic stem cells in the bone marrow.

Renin

• Decreased blood pressure, low sodium levels are the stimuli for the production of renin from the kidney.
• The renin secreted has enzymatic activity and is an important part of renin-angiotensin-aldosterone system (RAAS).
• The RAAS plays an important role in regulating the cardiac output and arterial pressure.
• The main function of renin in the RAAS system is the conversion of angiotensinogen to angiotensin I (proteolytic activity).

Calcitriol (1,25- dihydroxycholecalciferol)

• It is the active form of vitamin D.
• It stimulates the formation of calcium-binding protein thereby increasing the intestinal absorption of calcium.
• Thus, it plays an important role in the mineralization of the bone (bone formation)