Parathormone has all of the following effects, except –
**Core Concept**
Parathormone (PTH), also known as parathyroid hormone, is a hormone secreted by the parathyroid glands that plays a crucial role in maintaining calcium homeostasis in the body. It primarily acts on the bones, kidneys, and intestines to regulate calcium levels.
**Why the Correct Answer is Right**
Parathormone increases calcium levels in the blood by stimulating the release of calcium from bones, increasing renal reabsorption of calcium, and enhancing calcium absorption from the intestines. PTH also decreases phosphate levels in the blood by increasing its excretion in the urine.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the primary effect of PTH. While PTH does have some effects on the heart, its primary actions are on the bones, kidneys, and intestines.
**Option B:** This option is incorrect because PTH actually increases calcium levels in the blood, not decreases them. PTH's primary effect is to increase calcium levels.
**Option C:** This option is incorrect because PTH does have some effects on the kidneys, but the statement is too vague and does not accurately describe the specific effects of PTH on the kidneys.
**Clinical Pearl / High-Yield Fact**
PTH resistance can lead to conditions such as familial hypocalciuric hypercalcemia (FHH), where patients have elevated PTH levels and hypercalcemia despite normal or low calcium levels in the urine.
**Correct Answer: B. PTH decreases calcium levels in the blood.**