CaSR PTH Suppression — FRCA Primary MCQ
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Correct answer: B — Decreasing PTH secretion
When ionised calcium rises the CaSR on parathyroid chief cells is activated suppressing PTH secretion. When calcium falls reduced CaSR signalling increases PTH which then increases calcium via bone resorption / renal reabsorption / and stimulation of 1-alpha-hydroxylase. Calcitonin is produced by thyroid C-cells not the parathyroid.
Reference: Power Kam 2018 Principles of Physiology for the Anaesthetist