The Dorothy Hodgkin insulin structure breakthrough came in 1969, when her Oxford team mapped insulin's three-dimensional shape. She didn't discover insulin or determine its building-block order. Her team showed how the molecule was arranged in space, answering a different question about a medicine already in use.
The Dorothy Hodgkin insulin structure problem
Insulin is a hormone, a chemical messenger that helps control blood sugar. Its chains contain amino acids, the building blocks of proteins.
Frederick Sanger and his colleagues had established the sequence, the order of those blocks. The Nobel Foundation dates his identification of the links between insulin's chains to 1955. Hodgkin's question was how the chains fitted together in space.
How the team turned X-rays into a map
Hodgkin used X-ray crystallography: working out atomic arrangements from the patterns made when X-rays pass through a crystal. Crystals hold molecules in repeating arrangements. Her Nobel lecture explains how measurements and calculations became maps researchers could interpret.
The team's Nature paper, published November 1, 1969, reported an electron-density map, a calculated picture showing where atoms were likely to sit. It revealed details of insulin's arrangement inside the crystals.
Ten names appear on the paper. The byline lists M. J. Adams, T. L. Blundell, E. J. Dodson, G. G. Dodson, M. Vijayan, E. N. Baker, M. M. Harding, D. C. Hodgkin, B. Rimmer and S. Sheat, all at Oxford.
Why her Nobel Prize came before the insulin paper
Hodgkin received the 1964 Nobel Prize in Chemistry, five years before that paper. The prize recognized her X-ray work, including earlier achievements with penicillin and vitamin B12. Insulin was still unfinished work in her Nobel lecture.
Why exact structure matters: sermorelin
Hodgkin helped make molecular shape something researchers could investigate directly. Modern peptide research also asks which pieces matter and what changes do.
Sermorelin offers a simple example. A peptide is a short chain of amino acids. The National Library of Medicine identifies sermorelin as the active 29-building-block fragment of growth hormone-releasing hormone, or GHRH. That's the brain's signal asking the pituitary, a small gland beneath the brain, to release growth hormone.
Copying a defined fragment identifies the molecule being studied. The growth hormone discovery history follows the separate work on the hormone it helps release.
CJC-1295 and ipamorelin: different structures, different receivers
CJC-1295 is an analog, a deliberately modified version, of a GHRH fragment. In Jetté and colleagues' 2005 Endocrinology paper, its design included an attachment to albumin, a protein in blood. The study examined cultured rat cells and rats. The attachment helped the studied molecule remain in circulation longer.
Ipamorelin takes another route. Raun and colleagues' 1998 European Journal of Endocrinology paper described a five-building-block peptide acting through a different receptor, a cell's receiving site for a signal. Their experiments included rat cells, rats and pigs.
This is why the exact molecule matters even when two compounds affect growth hormone release. Similar destinations don't make their structures or receiving sites interchangeable. Those original experiments also didn't test a CJC-1295/ipamorelin blend in people.
Human studies were another step. Teichman and colleagues' 2006 trial report examined long-acting CJC-1295 in healthy adults. Researchers measured growth hormone and IGF-1, a blood protein whose level responds to growth hormone. They studied CJC-1295 alone, without ipamorelin.
That difference matters when reading a modern product description. Hormone measurements answer a narrower question than whether someone sleeps better or recovers faster. And studying one ingredient doesn't test the combination.
Knowing how each ingredient signals gives researchers a question to investigate together. It doesn't supply the answer about the combination's benefits or longer-term effects.
What came next for insulin itself
The insulin story kept moving. Hodgkin and colleagues returned to it in a 1976 Nature paper about another crystal form. They compared crystals containing different amounts of zinc, a metal involved in how insulin molecules group together.
The researchers reported a substantial difference in molecular shape hidden inside apparently similar crystal arrangements. The earlier map gave researchers a starting point for those comparisons. Seeing a molecule once hadn't answered every question about how it could be arranged.
This is one reason the conditions of an experiment matter. A structural study describes the arrangement found under those conditions. Later work can examine what changes when the surroundings change.
In vitro means outside a living body; in vivo means inside an animal or person. The in vitro versus in vivo guide explains why the setting matters. Neither label, by itself, establishes a benefit in patients.
Tesamorelin: keeping a longer chain
Tesamorelin makes another useful comparison. The Egrifta WR prescribing information, marked “Revised: 3/2025,” describes a molecule containing GHRH's full 44-amino-acid sequence with a chemical group attached at one end. It acts at the GHRH receptor.
Sermorelin copies an active fragment; tesamorelin keeps the longer sequence and modifies an end. Those are specific design choices. A shared receptor doesn't make two molecules identical or let one product's evidence answer every question about another.
The Egrifta WR label concerns excess abdominal fat in adults with HIV and abnormal fat distribution. HIV is a virus that affects immune cells. The label specifically says the product isn't indicated for general weight-loss management. That distinction comes from studies and product review, beyond the molecule's structural description.
What a structure cannot tell a patient
A molecular map helps explain which parts sit where. It doesn't measure a person's symptoms, unwanted effects or longer-term health. Those questions need studies designed to measure them.
Making a peptide is another separate achievement. The 1984 Nobel Prize for peptide synthesis concerns methods for building chains. Knowing a sequence, mapping its shape, making it and testing a treatment are connected jobs. None completes all the others.
That is the useful inheritance from Hodgkin's story: precise questions and credit for the people who answered them. Her insulin work didn't establish an anti-aging benefit for these later compounds.
Where the prescription decision sits
Sermorelin, CJC-1295/ipamorelin and tesamorelin prescribed through Promise are dispensed by a licensed U.S. compounding pharmacy as compounded medications, prepared for an individual prescription. Tesamorelin offered here is different from an FDA-approved product: an approved tesamorelin product exists for one narrow use, and the compounded formulation offered here is not FDA-approved. No FDA-approved sermorelin product is currently marketed — Geref's approvals, from 1990 and 1997, were withdrawn in 2009 — and the compounded formulation offered here is not FDA-approved. CJC-1295 and ipamorelin have never had an FDA-approved product, and the compounded blend offered here is not FDA-approved. FDA's compounding explanation distinguishes those preparations from products reviewed before marketing.
A licensed provider may still prescribe — that decision is between you and your doctor.
At Promise, a licensed provider reviews every request, and not everyone qualifies. If prescribed, a licensed U.S. compounding pharmacy prepares and dispenses the medication. The visit considers the person's history, the evidence for the intended use and follow-up, rather than a molecule's famous ancestry.
