- Video resources can be found at the following website: https://www.contraceptionmasculine.fr/la-methode-thermique-en-videos/#anneau (French language only)
- ANSM (Agence nationale de sécurité du médicament et des produits de santé). In English National Agency for the Safety of Medicines and Health Products. A French state agency.
- TESTIS_2021: Enquête transversale sur les dispositifs de contraception par remontée testiculaire : sécurité, acceptabilité, efficacité.. Dissertation defended on 11 January 2023 by Manon Guidarelli. (Text in French only).
Alternative contraceptive methods for men
Recently, there have been more attempts to introduce long-term contraceptive methods for men. One of them is thermal contraception. Dr. Alan Charissou expands on the method.
Key issues to know about thermal contraception
Translated from the original French version
Dr Charissou, how do male-targeted contraceptives work?
Charissou: Two methods consist of reversibly blocking sperm formation (as opposed to vasectomy). The aim is to fall below the limit of one million sperm per millilitre of ejaculate set by the WHO. Below this level, the probability of conception is just as low as with the highly effective methods already available (vasectomy, tubal ligation, intrauterine device, contraceptive implants).
To date, oral hormonal contraception does not work for men. All tested molecules are destroyed during liver transit. By contrast, weekly intramuscular injections of testosterone enanthate were successfully tested in the 1990s.
With regard to this first method, the WHO recommends using it for only 18 months - previous trials show - and providing contraception in parallel for the first three months until the blocking of spermatogenesis is established.
Testosterone enanthate is marketed in France. So men can resort to this hormonal contraceptive, but it is still quite unknown and there are very few doctors who can supervise these patients.
In terms of hormonal contraception for men, other avenues are being investigated. Phase 3 trials are currently underway for a skin gel that contains testosterone and is to be applied to certain parts of the body twice a day. A market launch is expected in 7 to 10 years at the earliest. Finally, the development of an implant, similar to that used by women, is also being researched.
The second method of contraception for men, this time non-hormonal, is thermal contraception. It consists of raising the temperature of the testicles to block spermatogenesis. This is done either by an exogenous heat supply - e.g. by warming underwear - or by using the body heat, which is 2° to 4° higher than that of the scrotum. This difference is small, but sufficient. The principle is simple: the more moderate the temperature rise, the longer the heat exposure should be.
Is thermal contraception a novel method?
Charissou: Not at all. The principle has been known for a long time. Hippocrates already observed that testicles kept warm affect fertility.
The pioneer of male contraception was Marthe Voegeli, a Swiss doctor. In the 1930s, she worked in India in her own private hospital. There, against a background of famine, she began research into reversible fertility limitation.
Volunteers bathed their testicles in a hot bath, 45 minutes a day, for three weeks. Voegeli observed that these men became temporarily infertile after the experiment, but were then able to have healthy children again.
The duration of infertility depended on the water temperature: a bath at 46.7 °C provided contraception for six months; a bath at 43.3 °C reduced the duration to four months.
From 1950 onwards, Marthe Voegeli devoted herself to popularising this method, but with little success. Later, the HIV epidemic brought male contraception experiments to a halt and the condom became the primary method.
What devices are used in thermal contraception?
Charissou: You can thermally insulate the scrotum to block its thermoregulation, with "insulating" briefs. However, so far this does not work very well. The most effective method is to pull up the testicles and stick them to the body.
Three devices are currently used in France: the Toulouse slip, the jockstrap and the silicone ring.1 None of them has yet received the European certification that any medical device needs in order to be marketed.
For the testicular lift to be effective, the device must be worn for at least 15 hours per day. The protocol is strict and requires that another contraceptive method be used in parallel for the first three months until the blockage of spermatogenesis is effective and confirmed by a control spermiogram. This examination must then be carried out every three months for as long as the method is used.
The Toulouse slip is an invention of the andrologist Roger Mieusset, who practices at the University Hospital of Toulouse. He is also a member of an association founded in 1979 by a dozen men from militant circles who wanted to contribute their share in contraception methods.
To this day, the Toulouse slip and jockstrap are not produced industrially. It is quite difficult to obtain them: You either have to go to the University Hospital of Toulouse for advice or make them yourself. In activist circles, there have been "sewing workshops" for more than ten years, where men explain to other men how to make a Toulouse slip or a jockstrap.
The result: the media went into overdrive about it and the French health authorities began to take an interest in this method and its devices.
The inventor of the Andro-Switch took a purely pragmatic approach: There was neither a clinical trial nor a test for compliance with CE standards [that is, the Conformité Européenne or CE quality certification used in the EU]. Finally, the French agency that assesses the health risks posed by medicines and health products banned the use of the ring at the end of 2021 - except in the context of clinical trials.2
Their reasons? The risk of unwanted pregnancy, "possible damage to the health of users, especially those with hypofertility factors", or even "health problems in children conceived with this contraceptive or in the six months following its discontinuation".
In your opinion, are these fears justified?
Charisson: There is little scientific work in the field of male contraception, as seen in the WHO pilot studies on intramuscular injections.
This research does not seem to be of interest to the funders, probably because it could produce contraceptive methods that compete with female hormonal contraception, whose market is sufficiently profitable for the pharmaceutical industry.
Therefore, we have little reliable clinical data on the possible risks of ascended testicles. Occasionally, an increase in the risk of developing testicular cancer is discussed. This fear is derived from a somewhat oversimplified link between undescended testis and cryptorchidism.
It is known that cryptorchid men have a sevenfold increased risk of developing testicular cancer. However, the analogy with undescended testis is not possible for two reasons.
The first reason is that in cryptorchidism immature testes are exposed to supra-scrotal temperature. In the case of thermal contraception, the testes are already in puberty. Still, there is a big difference.
Incidentally, epidemiological or experimental studies that have explored the effects of exposing pubescent testes to a temperature equivalent to that of the human body have never demonstrated an increased risk of testicular cancer.
The other reason is that research explaining the increased risk of testicular cancer in cryptorchid men has disqualified the thermal factor; it is not intra-abdominal heat exposure that is responsible for testicular cancer, but rather genetic or hormonal factors.
Another theoretical risk of thermal contraception is the alteration of DNA in sperm. Here, too, the data are lacking. However, a teratogenic risk can be very easily ruled out by instructing the men concerned to use another contraceptive in the six months after stopping thermal contraception.
This behaviour is quite similar to that already recommended in the use of teratogenic drugs already on the market, such as in the treatment of acne with isotretinoin.
Finally, it has been hypothesised that men who wear an andro-switch are at risk of urethral stenosis because the ring somewhat constricts the base of the scrotum. A recent retrospective study, the largest ever conducted on all testicular high-switches, is very reassuring on this point.
A young French doctor, Manon Guidarelli, as part of her PhD in public health, conducted a follow-up of 970 men who used thermal contraceptives. Some participants were followed for four years.3
Among the 900 participants who had been using the ring for at least six months, no case of urethral stenosis was reported. On the other hand, discomfort during passing water at the end of urination was reported in 20% of the cases. It is therefore recommended to remove the ring at the time of urination.
In this study, there was no unintended pregnancy in the partnership of participants who followed the protocol: 15 hours of daily wearing of the slips or the ring and a spermiogram every three months. In total, this corresponds to 3,752 exposure cycles.
You are a volunteer in the Entrelac.coop structure. What is your task?
Charisson: The main need at present for conducting major clinical trials on male contraception is funding. Entrelac.coop is a collective interest community; this legal form allows us to raise funds.
Since we cannot raise these funds in Europe, we have just applied for a grant from an American organisation, the Male Contraceptive Initiative. It is supported in particular by the Bill and Melinda Gates Foundation and offers funding for research into non-hormonal contraceptive methods.
The first project accompanied by Entrelac.coop aims to support European certification for the Andro-Switch. We have chosen to do this because this certification requires that the device be manufactured industrially. Of the current devices, only the silicone ring is at this stage of development. Later, Entrelac.coop hopes to be able to accompany all the other devices in this process.
In order to support the manufacturer of the Andro-Switch in obtaining European certification, we intend to carry out two studies. The first study will look at safety: 60 participants will use the ring for two years. We will conduct comprehensive monitoring of any adverse effects that may occur. The second study will look at the efficacy of the product. We are currently exchanging ideas with the ANSM to map out the protocols for this work.
Does male contraception have a feminist dimension?
Charisson: It has mainly a socio-political dimension. While male contraception can be of interest for women who find themselves in a contraceptive cul-de-sac, the current struggle of many women is mainly about the possibilities of gaining control over their own bodies. Feminist movements are therefore more committed to the development and dissemination of new contraceptive methods for women.
Contraception for men, on the other hand, remains a militant approach for many. Contraceptive briefs were developed by men after the May 1968 movement who were sensitised to feminist issues. They produced and tested the first models themselves.
This militant mindset can also be found in today's "Do It Yourself" workshops. There you can find sewing tips for briefs or plans for 3D printing moulds to make contraceptive rings.
Proportionally, the militant dimension of male contraception can be compared to that which surrounded the beginnings of zidovudine (AZT) in the 1980s. When this antiretroviral drug came on the market, it was available in the USA but not in Europe - on the grounds that there was not enough demand.
AIDS patients fought for access to this treatment and said, "Let's take the risk of testing this treatment". Today, many men are demanding access to thermal contraception, with or without the approval of the French health authorities.
Of course, the same issues are not at stake at present! AIDS was about death, here it is about unwanted pregnancies. But the men who choose this method, arguing that their bodies and health belong to them and that it is not up to the medical profession to decide in their place, are in the same way questioning the power of those treating, over the ones being treated, and the freedom to choose over their own bodies.
What is the role of doctors in terms of male contraception?
Charisson: You have to be pragmatic. Despite the ban and the cessation of sales of Andro-Switch by the Thoreme company, thousands of men in France continue to use the ring method. Either they make them in workshops or they procure them through unregulated distribution channels. A pair of heated boxer shorts is being also marketed.
Access to male contraception is becoming a major issue as more and more men now want to share the responsibility for contraception. Even French MPs are calling for exploring the possibility of male contraceptives distribution.
I think that doctors need to be able to inform and accompany men who want to start or continue with thermal contraception in the best possible way. Appropriate resources are available. In France, Planning familial (similar to the German Profamilia) has been offering counselling on male contraception since 2016, regardless of whether it is thermal or hormonal contraception.
Dr. Alan Charissou
Alan Charissou is a general practitioner who initially worked in public health before specialising in sexual and reproductive health. He is head of the working group "Contraception in Men" at the Collège de la Médecine Générale in Paris.
He also coordinates on a voluntary basis the research projects and medical communication activities of Entrelac.coop, a community created in 2022 to promote all forms of male contraception in France.