Medicine & USMLE

Parathyroid Hormone (PTH)

Endocrine & Hormones
  1. Leptin
  2. Ghrelin
  3. Protein Hormones
  4. Steroid Hormones
  5. Insulin
  6. Diabetes
  7. Glucagon
  8. Epinephrine
  9. Cortisol
  10. Thyroid Hormones
  11. Calcitonin
  12. Parathyroid Hormone (PTH)
  13. Anterior Pituitary
  14. Prolactin
  15. Luteinizing Hormone (LH)
  16. Follicle-Stimulating Hormone (FSH)
  17. Growth Hormone (GH)
  18. Posterior Pituitary


Parathyroid hormone, or PTH for short, is a protein hormone produced by the parathyroid gland. Parathyroid hormone functions to increase blood calcium levels. This means that it is released in response to low blood calcium levels, also known as hypocalcemia. Parathyroid hormone increases blood calcium in three ways. one, by acting on the kidneys to increase calcium reabsorption from urine. Two, by acting on osteoclasts to stimulate breakdown of bone, which releases calcium into the blood. And three, by increasing vitamin D production to increase calcium absorption from the intestines.

Key Points

  • Parathyroid Hormone (PTH)
    • Origin: Parathyroid
    • Type: Peptide
    • Trigger: Low blood calcium levels
    • Target: Bones and Kidneys
      • Effect:
        • Stimulates proliferation of osteoclasts
          • Osteoclasts break down bone so that the calcium can be utilized by the body
        • Increases renal calcium absorption
        • Increases calcium uptake in gut
        • Raises blood calcium levels
          • Opposite effect of calcitonin from the thyroid gland