HRT1, or Human Retinol-Binding Protein 1, is a protein that plays a crucial role in the transport of vitamin A (retinol) within the body. It is primarily produced in the liver and helps deliver retinol to various tissues, where it is essential for processes like vision, immune function, and skin health. This protein is part of a larger family of retinol-binding proteins and is vital for maintaining adequate levels of vitamin A, which is necessary for the proper functioning of photoreceptors in the retina and overall cellular health. Deficiencies in HRT1 can lead to various health issues related to vitamin A deficiency.