The parathyroid hormone (PTH) does not directly increase calcium in urine. Instead, PTH primarily functions to increase calcium levels in the blood.
While PTH doesn't directly cause increased calcium excretion in urine, it is important to understand how it affects calcium handling by the kidneys:
- PTH's role: PTH acts on the kidneys to increase calcium reabsorption back into the bloodstream, primarily in the proximal convoluted tubule and the ascending loop of Henle. This prevents calcium loss through urine.
- Indirect effect: If blood calcium levels are elevated due to excessive PTH (hyperparathyroidism), the kidneys may not be able to reabsorb all of it, leading to an increase in calcium excretion into the urine. However, this is a secondary effect, not the primary function of PTH.
In summary, PTH's main function is to raise calcium levels in the blood by increasing reabsorption in the kidneys, not excretion in urine. The information from the reference, "Effects of PTH on the Kidneys," supports this.
