This, however, raised the question whether the hypothalamic factor had a direct effect on the teeth or rather had an indirect effect characteristic of other hypothalamic hormones.

These vessels, the hypothalamo-hypophysial portal vessels, carry the hypothalamic factors to the adenohypophysis, where they bind to specific receptors on the surface of the hormone-producing cells.

Assuming that the hypothalamic factor was mediated through one of the major salivary glands, they found that this factor was biologically active when administered to rats with intact parotid glands but was wholly ineffective in rats that had the parotid glands removed.