A<unk>  is a committed precursor of a hormone consisting of peptide hormones synthesized together that has a minimal hormonal effect by itself because of its expression-suppressing structure, often created by protein folding and binding additional peptide chains to certain ends, that makes hormone receptor binding sites located on its peptide hormone chain segments inaccessible.<unk> s can travel the blood stream as a hormone in an inactivated form, ready to be activated later in the cell by post-translational modification. The body naturally produces<unk> s as a way to regulate hormone expression, making them an optimal storage and transportation unit for inactive hormones. Once<unk> s are needed to be expressed,<unk>  convertase, a protein, cleaves the<unk> s and separates them into one or more active hormones. Often in nature, this cleaving process happens immediately, and a<unk>  is quickly converted to a set of one or more peptide hormones. Examples of natural, human<unk> s include proinsulin and pro-opiomelanocortin, but the most widespread<unk> s in use are synthetic and labeled as anabolic steroid precursors, used as ergogenic or anabolic agents for muscle growth. A commonly consumed example of said precursors are androstenedione and androstenediol, both of which are currently banned substances in the United States. However, several illegal steroids, such as 3β-hydroxy-5α-androst-1-en-17-one, are still being produced legally under different chemical names, and the majority have not undergone clinical studies.
Prohormone
Xenohormone
Neurohormone
Hormone
Local hormone
Gastrointestinal hormone
Sex hormone
Neuropeptide