Analog.

A modified version of a molecule designed to alter its properties.

An analog is a structurally modified version of a parent molecule, engineered to change properties such as potency, receptor selectivity, stability, or half-life while retaining the core activity that made the parent interesting. Almost every peptide drug in wide use is an analog rather than the natural hormone, because natural hormones are usually cleared far too quickly to be practical. Semaglutide is an analog of human GLP-1 with amino-acid substitutions that resist enzymatic breakdown plus a fatty-acid chain that makes it bind to albumin in the blood, which together turn a hormone that survives minutes into a drug given weekly. Tesamorelin is an analog of GHRH modified for stability. Small changes matter enormously here: swapping a single amino acid at the site where an enzyme cuts can change how long a molecule survives by orders of magnitude. The misunderstanding worth correcting is that an analog is interchangeable with its parent hormone or with other analogs of the same parent. Different modifications produce different receptor selectivity, different tissue distribution, different duration, and different side-effect profiles, so evidence about one analog does not automatically transfer to another. Sequence similarity on a product page is not the same as equivalence in the body.