Together, the observations that, upon RP gavage, the plasma ROH content of LAL-deficient mice did not increase and that their plasma RE content was markedly reduced demonstrate that LAL is required for efficient nutritional availability of vitamin A. However, LAL is not limiting for circulating ROH:RBP4 levels, and, if absent, it does not provoke vitamin A deficiency. The gene discussed is RBP4; the disease is vitamin A deficiency.