are hormones proteins
Hormones have diverse chemical structures, mainly of 3 classes: eicosanoids, steroids, and amino acid derivatives (amines, peptides, and proteins). The glands that secrete hormones comprise the endocrine signaling system. Amino acid–based hormones (amines and peptide or protein hormones) are water-soluble and act on the surface of target cells via second messengers; steroid hormones, being lipid-soluble, move through the plasma membranes of target cells (both cytoplasmic and nuclear) to act within their nuclei. 1 Peptide hormones consist of a polypeptide chain; they include molecules such as oxytocin (short polypeptide chain) or growth hormones (proteins).  Amino acid-derived hormones and protein hormones are water-soluble and insoluble in lipids. Types of Hormones. Although there are many different hormones in the human body, they can be divided into three classes based on their chemical structure: lipid-derived, amino acid-derived, and peptide hormones (which includes peptides and proteins). Other hormones, including steroid and thyroid hormones, are lipid-soluble; to allow for their widespread distribution, these hormones must bond to carrier plasma glycoproteins (e.g., thyroxine-binding globulin (TBG)) to form ligand-protein complexes. Steroid hormones are insoluble in water; they are carried by transport proteins in blood. As a result, they remain in circulation longer than peptide hormones. For example, cortisol has a half-life of 60 to 90 minutes, whereas epinephrine, an amino acid derived-hormone, has a half-life of approximately one minute. 1 Amino acid-derived hormones also include thyroxine (produced by the thryoid gland) and melatonin (produced by the pineal gland).  Peptide hormones consist of a polypeptide chain; they include molecules such as oxytocin (short polypeptide chain) or growth hormones (proteins). Receptors for most peptide as well as many eicosanoid hormones are embedded in the plasma membrane at the surface of the cell and the majority of these receptors belong to the G protein-coupled receptor (GPCR) class of seven alpha helix transmembrane proteins. Hormones affect distant cells by binding to specific receptor proteins in the target cell resulting in a change in cell function. When a hormone binds to the receptor, it results in the activation of a signal transduction pathway. Like all peptides and proteins, peptide hormones and protein hormones are synthesized in cells from amino acids according to mRNA transcripts, which are synthesized from DNA templates inside the cell nucleus.
Yes