Final answer:
PTH decreases blood phosphate levels by increasing its excretion in urine, and also raises blood calcium levels by stimulating the conversion of vitamin D to its active form, thereby increasing calcium absorption in the gut.
Step-by-step explanation:
Parathyroid hormone (PTH) has a significant effect on phosphate (PO4) levels in the blood. In responding to low blood calcium levels, PTH is released from the parathyroid gland. This hormone has multiple actions; one of which is to decrease PO4 concentration in the blood by increasing its excretion through the kidneys.
Thus, PTH increases the loss of phosphate in urine. Additionally, PTH stimulates the conversion of vitamin D to its active form, calcitriol, which in turn increases the absorption of dietary calcium in the gastrointestinal tract, but not phosphate, aiding in maintaining calcium homeostasis.