Detailed Explanation
84-amino-acid peptide hormone produced by the parathyroid glands that is the primary regulator of blood calcium levels. When calcium drops, PTH is secreted and acts on three targets: it stimulates osteoclast-mediated bone resorption (releasing calcium from bone), increases renal calcium reabsorption and phosphate excretion, and stimulates the kidney to produce active vitamin D (calcitriol), which increases intestinal calcium absorption.
Paradoxically, intermittent low-dose PTH stimulates bone formation rather than resorption. This led to teriparatide (Forteo), a recombinant PTH fragment (amino acids 1–34), approved for osteoporosis — one of the few drugs that actually builds new bone rather than just slowing bone loss.
Key Facts
- 84-amino-acid peptide hormone produced by the parathyroid glands that is the primary regulator of blood calcium levels.
- When calcium drops, PTH is secreted and acts on three targets: it stimulates osteoclast-mediated bone resorption (releasing calcium from bone), increases renal calcium reabsorption and phosphate excretion, and stimulates the kidney to produce active vitamin D (calcitriol), which increases intestinal calcium absorption.
- Paradoxically, intermittent low-dose PTH stimulates bone formation rather than resorption.
- This led to teriparatide (Forteo), a recombinant PTH fragment (amino acids 1–34), approved for osteoporosis — one of the few drugs that actually builds new bone rather than just slowing bone loss.
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