Background <p>A long-term high-fat diet (HFD) leads to excessive lipid deposition, which may cause many diseases, including NAFLD, diabetes, and thyroid dysfunction. In addition, HFD leads to a decrease in serum growth hormone (GH) levels to further increase lipid deposition and obesity. However, the mechanism of such reduction of GH has not been fully elucidated.</p> Methods <p>Male Sprague-Dawley rats were fed a regular diet (CD) or a high-fat diet (HFD) for 29 weeks. GH synthesis and secretion were evaluated in pituitary and blood samples, respectively. An in vitro model was constructed by treating cultured cells with palmitic acid (PA). Vit D receptor (VDR) plasmids (OE-VDR), paricalcitol and VDR knockdown virus (sh-VDR) were used to overexpress or depress the activation of VDR during PA treatment of GH3 cells. The GH content, lipid content, and relevant expression of different molecules were measured in pituitary and cell samples.</p> Results <p>A HFD decreased the levels of circulating GH and the expression of Gh in the anterior pituitary gland tissues of rats. In vitro, PA treatment decreased Pit1 and Gh expression in cultured GH3 cells. VDR expression was reduced in the rat pituitary tissues under HFD conditions and in PA-treated GH3 cells. The overexpression and knockdown of VDR increased and decreased the expression of Pit1 and Gh, respectively. Paricalcitol antagonized the decrease in the expression of Pit1 and Gh caused by PA treatment.</p> Conclusions <p>HFD induced lipid deposition in the pituitary may cause GH deficiency, and VDR - Pit1 may be at least partially involved in the process.</p>