Calcitonin does not decrease Ca2+ in the blood by building bone but rather by excreting it through the kidneys or by inhibiting osteoclasts
I know this Anki card is a bit long, but I don't think it can be shortened while retaining the relevant info. If you can, be my guest.
UWorld supports this information. QID: 400978 I got it from one of the educational objective for one of the questions:
Educational objective:
Calcitonin, a hormone synthesized by the thyroid gland, decreases calcium concentrations in the blood by inhibiting osteoclast activity (bone resorption) and promoting calcium excretion in the kidneys
Open to considering this for the Extra field, but big changes to Text field need to be accompanied by significantly compelling rationale. Right now, the details are fine, though they're a significant departure from the existing card (which is correct according to a primary source). This might be a good candidate for a new card, rather than a wholesale wipe of an existing card. And/or feel free to add a suggestion in which we delineate this info in the Extra field. Open to ideas.