Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist licensed in the UK for type 2 diabetes and weight management. Whilst Mounjaro and ovarian cysts are not directly linked in clinical evidence, significant weight loss and metabolic improvements may influence reproductive hormones and menstrual patterns. Women using Mounjaro may experience hormonal rebalancing that can affect ovulation and, consequently, the development of functional ovarian cysts. Understanding this relationship helps patients recognise when symptoms require medical assessment and ensures safe, informed use of this medication alongside comprehensive reproductive health monitoring.

What Is Mounjaro and How Does It Work?

Mounjaro (tirzepatide) is a prescription medicine licensed in the UK for the treatment of type 2 diabetes mellitus and, more recently, for weight management in adults with obesity (BMI ≥30 kg/m²) or overweight (BMI ≥27 kg/m²) with at least one weight-related comorbidity. It is administered as a once-weekly subcutaneous injection and represents a novel class of medication known as a dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist.

The mechanism of action of Mounjaro involves mimicking two naturally occurring incretin hormones that play crucial roles in glucose regulation and appetite control. By activating both GIP and GLP-1 receptors, tirzepatide enhances insulin secretion in a glucose-dependent manner, suppresses glucagon release when blood glucose levels are elevated, slows gastric emptying, and reduces appetite. This dual action contributes to improved glycaemic control in people with type 2 diabetes and significant weight loss in those using it for weight management.

Mounjaro is typically initiated at a low dose (2.5 mg weekly) and gradually increased over several weeks to minimise gastrointestinal side effects, which are among the most commonly reported adverse reactions. These include nausea, vomiting, diarrhoea, and constipation. Patients should report suspected side effects via the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk).

Important safety considerations include seeking urgent medical care for severe, persistent abdominal pain (which may indicate pancreatitis or gallbladder disease), maintaining adequate hydration to prevent acute kidney injury, and monitoring for hypoglycaemia if used with insulin or sulfonylureas.

Tirzepatide can reduce the effectiveness of oral hormonal contraceptives. Women using these contraceptives should consider using a non-oral method or adding a barrier method for 4 weeks after starting treatment and for 4 weeks after each dose increase. Mounjaro is not recommended during pregnancy and should be discontinued at least 1 month before a planned pregnancy. It should also be avoided during breastfeeding.

Patients prescribed Mounjaro should receive comprehensive counselling about proper injection technique, storage requirements, and the importance of adhering to dose escalation schedules. It is essential that individuals discuss their complete medical history with their healthcare provider before starting treatment, as certain conditions may require additional monitoring or preclude its use.

Understanding Ovarian Cysts: Causes and Symptoms

Ovarian cysts are fluid-filled sacs that develop on or within the ovaries. They are extremely common, particularly in women of reproductive age, and most are functional cysts that form as a normal part of the menstrual cycle. These functional cysts typically resolve spontaneously within 2-3 menstrual cycles without requiring medical intervention.

There are several types of ovarian cysts:

• Follicular cysts develop when the follicle that normally releases an egg fails to rupture and continues to grow

• Corpus luteum cysts occur when the corpus luteum (the structure that forms after ovulation) fills with fluid or blood

• Dermoid cysts (teratomas) arise from germ cells and contain tissue such as hair, skin, or teeth; they may be present from birth but often present during reproductive years

• Cystadenomas develop from ovarian tissue and may be filled with watery or mucous material

• Endometriomas result from endometriosis, where endometrial tissue grows on the ovaries

Many ovarian cysts produce no symptoms and are discovered incidentally during pelvic examinations or imaging for other reasons. When symptoms do occur, they may include:

• Pelvic pain or a dull ache in the lower abdomen

• Bloating or abdominal swelling

• Pain during intercourse

• Irregular menstrual periods or changes in menstrual flow

• Difficulty emptying the bladder completely

• Pressure on the bowel leading to difficulty passing stools

Risk factors for developing ovarian cysts include hormonal imbalances, pregnancy (corpus luteum cysts are common in early pregnancy), endometriosis, pelvic infections, polycystic ovary syndrome (PCOS), and fertility treatments. Previous ovarian cysts also increase the likelihood of developing further cysts. Most functional cysts are benign and pose no serious health risk, though larger cysts or those that persist may require further investigation to exclude other pathology.

When to Seek Medical Advice About Ovarian Cysts

While most ovarian cysts are harmless and resolve without treatment, certain symptoms warrant prompt medical attention. It is important to recognise warning signs that may indicate complications such as cyst rupture, ovarian torsion (twisting), or, rarely, malignancy.

Seek urgent medical care (attend A&E or call 999) if you experience:

• Sudden, severe pelvic or abdominal pain – this may indicate a ruptured cyst or ovarian torsion, both of which require immediate assessment

• Pain accompanied by fever or vomiting – these symptoms may suggest infection or a surgical emergency

• Dizziness, weakness, or fainting – particularly if associated with pelvic pain, as this could indicate internal bleeding from a ruptured cyst

• Shoulder tip pain – may indicate blood irritating the diaphragm from a ruptured cyst

• Signs of haemodynamic instability – such as rapid pulse, low blood pressure, or feeling faint

Contact your GP for a routine appointment if you notice:

• Persistent pelvic pain or discomfort that does not resolve

• Changes in your menstrual cycle, including irregular periods or unusually heavy bleeding

• Difficulty emptying your bladder or frequent urination

• Persistent bloating or abdominal swelling

• Pain during sexual intercourse

Your GP will typically perform a pelvic examination and may arrange an ultrasound scan to visualise the cyst and determine its size, type, and characteristics. According to Royal College of Obstetricians and Gynaecologists (RCOG) guidance, most simple cysts under 5 cm in premenopausal women can be managed conservatively without follow-up. For cysts 5-7 cm, interval ultrasound may be considered, while cysts larger than 7 cm may require MRI or surgical opinion.

If you have persistent or frequent symptoms suggestive of ovarian cancer, your GP may check a blood test called CA125. If this is elevated (≥35 U/ml), they will arrange an urgent ultrasound and consider a suspected cancer (2-week-wait) referral if the ultrasound findings are suspicious. It's important to note that CA125 is not a screening test and can be raised in many benign conditions, especially in premenopausal women.

Regular monitoring and open communication with your healthcare provider ensure that any concerning changes are identified early and managed appropriately.

Can Mounjaro Affect Ovarian Cysts?

Currently, there is no established clinical evidence linking Mounjaro (tirzepatide) directly to the development or worsening of ovarian cysts. Ovarian cysts have not been identified as a recognised adverse effect in the clinical trials conducted for Mounjaro's approval, nor are they listed in the Summary of Product Characteristics (SmPC) approved by the MHRA or European Medicines Agency (EMA).

However, it is important to consider the indirect effects that significant weight loss and metabolic changes may have on reproductive health. Women with obesity often experience hormonal imbalances, including elevated androgens and insulin resistance, which can contribute to conditions such as polycystic ovary syndrome (PCOS) and irregular menstrual cycles. As Mounjaro facilitates substantial weight loss and improves insulin sensitivity, these metabolic improvements may actually lead to normalisation of hormonal function and restoration of regular ovulation in some women.

This hormonal rebalancing can result in changes to menstrual patterns, and in some cases, women may become aware of ovarian cysts that were previously asymptomatic or undiagnosed. Additionally, the restoration of regular ovulation increases the likelihood of developing functional ovarian cysts, which are a normal part of the ovulatory cycle.

It is also worth noting that weight loss itself can influence reproductive hormones. Adipose tissue plays a role in oestrogen production, and significant changes in body composition may temporarily affect the menstrual cycle and ovarian function during the weight loss phase.

Importantly, weight loss and improved insulin resistance may restore ovulation and increase fertility. Women who do not wish to become pregnant should ensure they are using effective contraception. As mentioned earlier, tirzepatide can reduce the effectiveness of oral hormonal contraceptives, so women should consider using a non-oral method or adding a barrier method for 4 weeks after starting treatment and for 4 weeks after each dose increase. If pregnancy is planned, tirzepatide should be discontinued at least 1 month before conception. If you become pregnant while taking Mounjaro, you should discontinue it and inform your healthcare provider promptly.

Patient advice: If you are taking Mounjaro and develop symptoms suggestive of ovarian cysts—such as pelvic pain, bloating, or menstrual irregularities—contact your GP for assessment. These symptoms should be evaluated on their own merits rather than automatically attributed to the medication. Your healthcare provider can arrange appropriate investigations, including pelvic ultrasound if indicated, to determine the cause and guide management. Always inform your doctor of all medications you are taking, including Mounjaro, to ensure comprehensive care and appropriate monitoring of your overall health.

Frequently Asked Questions