The weight loss medicine market is booming. Estimated at $161.12bn globally in 2024, it’s expected to grow by nearly 125% in the next ten years.
Less than two years after Wegovy and Mounjaro were approved to treat obesity in the UK, there are now an estimated 500,000 people taking them.
However, like most new medicines, weight loss drugs haven’t come without their criticisms. It seems every week, there’s a new article about side effects, possible interactions and complication concerns.
But lately, we have seen stories from women who claim to have gotten pregnant while taking weight loss medications despite being on oral contraceptives.
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While evidence about this specific interaction remains limited, there are ongoing conversations about how it may impact female reproductive health overall, and how weight loss medications like Wegovy can impact everything from periods to sexual desire to fertility and pregnancy and why it might soon be introduced as an effective treatment for Polycystic Ovary Syndrome (PCOS).
Irregular
GLP-1 receptor agonists such as Semaglutide (Wegovy) and Tirzepatide (Mounjaro) have completely changed weight management. But the way they work goes beyond appetite regulation. By influencing energy balance and hormonal pathways, these treatments can indeed lead to irregular menstrual cycles, an important note for pharmacists and healthcare professionals advising patients.
Reproductive function is closely linked to energy availability. Rapid fat loss can disrupt hypothalamic-pituitary-ovarian axis signalling, leading to lighter, delayed, or absent periods.
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While clinical data on menstrual irregularities with GLP-1 therapies remains limited, real-world reports show this trend needs further investigation. We do need to be counselling patients to monitor cycle changes and flag persistent irregularities for medical assessment, particularly in those considering pregnancy.
As weight loss treatments induce a sustained caloric deficit, the hypothalamus may downregulate gonadotropin-releasing hormone (GnRH) secretion, reducing luteinising hormone (LH) and follicle-stimulating hormone (FSH) output. The resulting disruption to ovulatory function can significantly impact fertility, particularly in women with pre-existing reproductive challenges.
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Clinical observations suggest that a reduction in body weight by more than 10% may lower conception rates by 30-40%, primarily due to anovulation. Plus, patients reaching a body fat percentage below 17% risk further endocrine disruption, including reduced oestrogen synthesis.
Current recommendations advise stopping GLP-1 receptor agonists at least two months before attempting conception. We, and our teams, should ensure patients receive appropriate preconception counselling, particularly regarding the timeline for ovulatory recovery post-treatment.
PCOS advantage
Polycystic Ovary Syndrome (PCOS) affects approximately 1 in 5 women in the UK and remains a major driver of anovulatory infertility. As insulin resistance is a core component of PCOS pathophysiology, GLP-1 receptor agonists are being considered as potential adjuncts in managing the condition.
Semaglutide’s ability to enhance insulin sensitivity and reduce hyperinsulinaemia may help restore ovulatory function, mitigate androgen excess, and support weight loss—key therapeutic goals in PCOS management.
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Early clinical trials suggest that GLP-1 therapies may complement existing interventions such as metformin and lifestyle modification. However, further large-scale studies are required to establish long-term efficacy and safety profiles in this cohort.
GLP-1 agonists aren’t currently licensed to treat PCOS, but there’s a suggestion this might be the next license in the pipeline for Mounjaro, and we may see that within the next year or two.
Libido
Beyond metabolic and reproductive effects, weight loss medications may also influence sexual function. Improved body image, enhanced insulin sensitivity, and hormonal regulation can contribute to increased libido and sexual satisfaction in some individuals.
However, the opposite effect is also possible. Reports of transient reductions in sexual desire during the initial phase of treatment may be linked to energy restriction, stress responses, or neurohormonal adaptations.
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Pharmacists should be prepared to discuss these potential side effects with patients and differentiate between physiological changes and psychosocial factors. Encouraging ongoing monitoring and providing reassurance that any sexual health concerns should be addressed in follow-up consultations can enhance patient adherence and satisfaction.
Future investigations
As the clinical use of GLP-1 receptor agonists continues to expand, their impact on reproductive health will be investigated further.
While these medications offer significant advantages for weight management and metabolic control, healthcare professionals must remain vigilant about their broader physiological effects.
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From menstrual irregularities and ovulatory suppression to emerging applications in PCOS management, understanding these implications allows pharmacists and prescribers to optimise patient care, provide informed counselling, and mitigate potential risks.
Remember also that Wegovy, Mounjaro and all new weight loss medicines are black triangle drugs. Any and all reported side effects, reproductive or otherwise, must be reported via the MHRA yellow card scheme.
Kiran Jones is clinical pharmacist at Oxford Online Pharmacy