Glucagon-like peptide-1 (GLP-1) is an incretin hormone. It is derived from the posttranslational processing of proglucagon. This prohormone is synthesized by three cell populations, the neuroendocrine L cells of the intestinal mucosa, the ß cells of the pancreatic Langerhans islands and in a neuronal population located in the nucleus tractus solitarii (NTS) and intermediate reticular nucleus of the medulla oblongata.
While the HPT axis warrants the stability of circulating thyroid hormone levels, a complex machinery of thyroid hormone transporters, metabolizing enzymes, receptors and co-regulators ensures that the local thyroid hormone action meets the highly variable requirements of the different tissues.
The hypothalamic-pituitary-thyroid (HPT) axis primarily functions to maintain normal, circulating levels of thyroid hormones that are essential for the biologic function of all tissues including brain development, regulation of cardiovascular, bone and liver function, food intake and energy expenditure among many others.
