L-Alloisoleucine (L-allo-Isoleucine) is a branched chain amino acid and is a stereoisomer of L-isoleucine. It is a common constituent of human plasma (albeit at low levels). L-alloisoleucine is produced as a byproduct of isoleucine transamination. Plasma L-alloisoleucine, which is derived from L-isoleucine in vivo, can be used for the diagnosis of maple syrup urine disease (MSUD), a genetic disorder. Indeed, plasma L-alloisoleucine levels above 5 μmol/L is the most specific and most sensitive diagnostic marker for all forms of MSUD.

Glycerol 3-phosphate biscyclohexylammonium salt is an endogenous metabolite produced by cytosolic glycerol 3-phosphate dehydrogenase pathway.

Liothyronine (Tresitope) is an active form of thyroid hormone, binding to β1 thyroid hormone receptor (TRβ1), and activates its activity.

Purine (7H-Imidazo(4,5-d)pyrimidine) is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring. Two of the bases in nucleic acids, adenine and guanine, are purines. Purines from food (or from tissue turnover) are metabolised by several enzymes, including xanthine oxidase, into uric acid. High levels of uric acid can predispose to gout when the acid crystalises in joints; this phenomenon only happens in humans and some animal species (e.g. dogs) that lack an intrinsic uricase enzyme that can further degrade uric acid.

Vasopressin (argipressin), a cyclic nine-peptide synthesized by hypothalamic neurons, is one of the hormones involved in peptide prohormone synthesis. Vasopressin is involved in the regulation process of hypothalamic-pituitary-adrenal axis, increasing the amount of solute free water reabsorbed from the renal tubule's colate back into the circulation, narrowing arteries to increase pressure, enhancing the stimulating effect of corticotropin releasing factor to regulate pituitary corticotropin secretion. Vasopressin acts as a neurotransmitter during nerve conduction by binding to specific G-protein-coupled receptors.