This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology and Reproduction, Subject name: Physiology
Steroid involved in water balance: 
Select and explain. 
A. Oestrogen, B. Testosterone, C. Aldosterone, D. Vit D
C: Aldosterone
Answer: C: Aldosterone 
Explanation: Ans: c (Aldosterone)Ref: Ganong, 23rd ed Pg. 357Aldosterone is the steroid that is mainly involved in water balance.AldosteroneIt increases the reabsorption of Na and excretion of K .It acts on the kidney - primarily the Principal cells of the collecting duct. Stimuli for secretion -Rennin angiotensin systemIncreased K -Endothelin -Low sodium -Standing -Stress like anxiety, surgery, trauma and hemorrhage