**Question:** Propey of elution is found in -

A. Small intestine
B. Liver
C. Kidney
D. Lung

**Core Concept:**

Protein Y (Protein Y of elution) is a hormone secreted by the parathyroid gland in response to low calcium levels in the blood, aiming to increase calcium levels. It acts on the bones, increasing resorption of calcium and phosphate, and on the kidneys, enhancing calcium reabsorption. This helps maintain calcium homeostasis in the body.

**Why the Correct Answer is Right:**

The correct answer, Propey of elution, is found in the liver. Protein Y is synthesized and secreted by the parathyroid gland in response to low calcium levels. When the hormone reaches the liver, it is processed and transported to its target organs: bones and kidneys. In the bones, Propey of elution stimulates bone resorption, releasing calcium and phosphate into the bloodstream. In the kidneys, it enhances calcium reabsorption, preventing calcium loss in urine.

**Why Each Wrong Option is Incorrect:**

A) Small intestine: Protein Y does not play a role in calcium absorption from the intestine. This function is primarily regulated by vitamin D and calcium-sensing receptor in the intestine.

B) Liver: Although Propey of elution is synthesized in the liver after being processed from parathyroid hormone, its primary action is at the bone and kidney level, as explained above.

C) Kidney: Protein Y does contribute to calcium reabsorption in the kidney, but the main reabsorption processes are regulated by the distal nephron and the action of active and passive transport mechanisms.

D) Lung: Propey of elution is not involved in calcium regulation in the lungs; this function is primarily regulated by the respiratory system and oxygen levels.

**Clinical Pearl:**

Understanding the action of Propey of elution helps medical students appreciate the complex interplay between calcium regulation and the involvement of various organs in maintaining calcium homeostasis. In clinical practice, knowledge of this hormone may be useful in interpreting calcium and parathyroid hormone levels in cases of hypocalcemia and hypercalcemia, as well as assessing the overall health of the parathyroid gland and calcium homeostasis.