An eight-minute sexual video gave researchers a way to test kisspeptin in men with distressing low desire. During one visit, each participant received the hormone through an intravenous infusion. During another, he received a placebo. Researchers measured brain activity and the physical response to what he watched.
By the end of the video, the measured increase in penile swelling was up to 56% greater with kisspeptin than with placebo. That figure came from a short laboratory experiment. Understanding the experiment matters if you are deciding how much weight to give a claim about a libido treatment. Mills et al., JAMA Network Open, 2023
Kisspeptin already had a substantial job in human biology: it helps activate the hormone signals needed for reproduction. The trial explored whether that same molecule could alter the brain's response to sexual cues in people whose desire had become a problem.
The finding raises a useful question: can a hormone that coordinates reproduction help restore the experience of wanting sex? The answer requires looking at what participants felt, as well as what the instruments recorded.
The name began with chocolate and cancer research
In 1996, Danny Welch's laboratory at Penn State's College of Medicine in Hershey was studying genes that could suppress the spread of melanoma cells. The team identified a gene called KISS1. Its name paid tribute to Hershey's chocolate Kisses, according to Welch and his coauthors' later account of the discovery.
The gene provides instructions for a protein that can be cut into shorter peptides. These fragments became known as kisspeptins. The number in a name such as kisspeptin-54 refers to the length of that peptide's amino-acid chain. Kisspeptin-10 has ten amino acids. Harihar et al., discovery history
That history gives the name some charm. The human experiments discussed here used kisspeptin-54, a specific molecule delivered under controlled conditions. Keeping its identity attached to the results becomes useful when you encounter products sold under the broader word “kisspeptin.”
Kisspeptin helps start a reproductive hormone signal
In the hypothalamus, a part of the brain that helps regulate hormone function, kisspeptin activates nerve cells that release gonadotropin-releasing hormone, usually shortened to GnRH. GnRH signals the pituitary gland to release luteinizing hormone and follicle-stimulating hormone, or LH and FSH.
These signals help coordinate reproductive function. In women, an LH surge helps trigger the final maturation of an egg. Researchers tested whether kisspeptin could provide that trigger during IVF, the process in which eggs are fertilized outside the body.
In a 2014 study, 53 women received kisspeptin-54 after other medicines had stimulated their ovaries. Eggs were collected 36 hours later. Fertilization and embryo transfer occurred in 49 women; ten eventually gave birth to twelve babies, including two sets of twins.
The study tested different kisspeptin doses without a standard-treatment comparison group. It showed that the hormone could serve as one step in an IVF protocol. It did not establish superior pregnancy outcomes. Jayasena et al., JCI, 2014
Conceptual illustration of the hormone sequence described by Jayasena and colleagues. The diagram omits feedback loops and does not represent a treatment protocol.
The brain has another task related to reproduction: processing the cues that make sexual activity appealing. Kisspeptin and its receptor had also been found in brain regions involved in emotion and behavior. That distribution gave researchers a reason to ask what the hormone might do beyond the reproductive hormone sequence.
The first brain study separated the response from a testosterone rise
In 2017, Alexander Comninos and colleagues reported an experiment involving 29 healthy young men. Each man attended two visits, receiving kisspeptin during one and a placebo solution during the other. Neither the participants nor the imaging analysts knew which infusion they were assessing.
The men viewed several kinds of images inside a functional MRI scanner. Some showed sexual content; others showed couples together without sexual activity. The researchers also used other emotional images and tasks as comparisons.
Functional MRI detects changes related to blood oxygenation. Researchers use that signal to study which regions respond during a task. A colored area on one of these maps represents a statistical comparison across observations. It cannot reveal a person's private thoughts.
With kisspeptin, certain brain regions responded more strongly to sexual images. These included parts of the cingulate cortex and the left amygdala, areas involved in emotional and behavioral processing. The response to couple-bonding images also changed. The hormone did not simply increase activity during every task.
Comninos et al., JCI 2017, Figure 2A, reproduced under CC BY 4.0. The panel shows the study's brain-activity comparison during sexual images. Colors do not measure how much desire an individual felt.
The timing mattered. The scans and questionnaires took place before testosterone increased. That helped the researchers examine kisspeptin's effects without a simultaneous testosterone rise explaining the findings. The study also found no overall change in the questionnaire domains measuring sexual arousal and desire. Comninos et al., JCI, 2017
These were healthy volunteers. A clinical question remained: would people distressed by low desire show a useful response?
The later trial enrolled men who wanted their desire to change
The 2023 study enrolled men with hypoactive sexual desire disorder, or HSDD. The diagnosis concerns low desire that causes distress. The research team screened participants for other conditions that could complicate the experiment, including underlying erectile dysfunction. Their testosterone levels were within the normal range.
Of 37 men randomized, 32 completed the trial. Each received a 75-minute kisspeptin-54 infusion on one visit and placebo on the other, at least a week apart. The order was randomized. Using the same participant for both conditions helped control for differences between people.
During the scans, the men watched short sexual clips alternating with exercise clips. They also watched one continuous eight-minute sexual video. The scanner measured brain responses; a separate device recorded changes in penile swelling, called tumescence. Participants also reported their subjective arousal.
The study found changes in brain regions involved in processing the sexual material. Its physical-arousal analysis included 30 men and showed a larger response during kisspeptin administration. The largest difference appeared at the end of the eight-minute video.
Mills et al., JAMA Network Open 2023, Figure 3A, reproduced under CC BY. The original chart shows normalized physical-response measurements in 30 men. KP means kisspeptin; the marker “a” denotes the overall comparison, P = .002. Error bars show the standard error of the mean. The reported 56% difference refers to the largest separation at the end of the task.
The 56% describes the relative size of a measured physical response at that point in the experiment. It is not the percentage of men whose low desire resolved. The trial did not follow participants through months of treatment to measure improvements in their sex lives. Mills et al., full trial
What the participants reported adds an essential part of the result
In the men's trial, kisspeptin improved the response to an individual questionnaire item about feeling happy about sex. It also increased reported flushing. The broader questionnaire domains did not change significantly. Testosterone remained unchanged during the study period.
A separate trial, published in 2022, examined 32 premenopausal women with HSDD who completed both visits. They received kisspeptin and placebo on separate days and underwent brain imaging while viewing erotic videos and faces.
Kisspeptin changed activity in several brain regions. Overall questionnaire domain scores again did not improve. An exploratory analysis found a higher rating on a single item asking how sexy the participant felt. The authors said that finding needed confirmation in dedicated studies. Thurston et al., JAMA Network Open, 2022
These results support further investigation. They also show why the outcome must stay attached to the claim. A brain response, a physical measurement and a reported feeling each describe a part of the experience. Lasting relief from distress would require follow-up designed to measure it.
No adverse events were reported in the short men's trial. That observation leaves questions about repeated use and longer exposure. A treatment someone uses at home would also need evidence for its formulation and delivery method. An infusion study cannot establish that every spray or injection sold with the same peptide name produces the same result.
How to discuss low desire with a clinician
If low desire is bothering you, describe the change to a clinician in concrete terms. When did it start? Does the concern involve wanting sex, physical arousal, pain, or the experience of sex itself? Mention medicines and other health changes. The details help define what a useful treatment outcome would be.
When you read a kisspeptin claim, find the study behind the number. Check whether it measured a response during one visit or a change that lasted through ordinary life. Look for the actual formulation and route used. Those details tell you how closely the evidence matches the treatment being offered.
The early studies give researchers a reason to keep working on kisspeptin. For a reader seeking help now, the useful next step is to make the desired improvement explicit and ask how a proposed treatment has been shown to deliver it.
Reply with the question about hormone research you want me to investigate next. No personal health details needed.
For entertainment and education only. Not medical advice. Talk to your doctor before starting anything.