Parathyroid hormone increases dietary calcium absorption by prompting the kidneys to make what?

1. Bone and kidney handling alone would not add new calcium to the body. 2. Parathyroid hormone therefore also initiates production of calcitriol in the kidneys. 3. Calcitriol is the active form of vitamin D3, also written as 1,25-dihydroxyvitamin D. 4. Calcitriol acts on the intestines to increase absorption of dietary calcium. 5. Calcitonin is the thyroid hormone that opposes all of this, so it cannot be the mediator. 6. Erythropoietin from the kidneys answers to low oxygen, and angiotensin belongs to the blood pressure pathway. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 17 "The Endocrine System", section 17.5 The Parathyroid Glands_