A little bit of a quibble here. Almost all of our Vitamin D in nature is not dietary in origin, but comes from skin exposure to UV light of a specific wavelength that is needed to cleave the B ring of dihydrotachysterol to pre-Vitamin D3, which is then hydroxylated in the liver to the main storage form, 25-hydroxycholecalciferol. They did not depend on dietary sources because they will I presume have had plenty of sunlight exposure at least in summer. The active form is 1,25 dihydroxycholecalciferol, which many tissues produce locally, and systemically is produced in the kidney under the action of parathyroid hormone, which is secreted in response to a fall in circulating ionised calcium, and acts on the small intestine to promote calcium absorption.
A giant with prognathism has excess growth hormone until proved otherwise