Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist licensed in the UK for type 2 diabetes mellitus, with significant weight-loss effects. As patients achieve substantial weight reduction, questions arise about Mounjaro's effect on testosterone and other hormones. Emerging evidence suggests that weight loss from tirzepatide may influence testosterone levels, though the relationship differs between men and women. In men with obesity, weight reduction often raises testosterone towards normal ranges, whilst women with polycystic ovary syndrome may experience beneficial reductions in elevated androgens. Understanding these hormonal changes is important for safe, effective treatment management.
Quick Answer: Mounjaro (tirzepatide) does not directly affect testosterone production, but significant weight loss achieved through treatment may increase testosterone in men with obesity-related low levels and reduce elevated testosterone in women with PCOS.
Mounjaro (tirzepatide) is a prescription medicine licensed in the UK for the treatment of type 2 diabetes mellitus. The same active ingredient, tirzepatide, is also marketed as Zepbound for weight management in adults with obesity or overweight with weight-related comorbidities. It belongs to a novel class of medications known as dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonists. This dual mechanism distinguishes tirzepatide from other GLP-1 receptor agonists such as semaglutide.
The medication works by mimicking the action of two naturally occurring incretin hormones. GLP-1 stimulates insulin secretion when blood glucose levels are elevated, suppresses glucagon release (which reduces glucose production by the liver), slows gastric emptying, and promotes satiety through central nervous system pathways. GIP also enhances insulin secretion and may influence fat metabolism and energy expenditure, though the precise mechanisms in humans remain under investigation. Together, these actions lead to improved glycaemic control and significant weight loss in many patients.
Mounjaro is administered as a once-weekly subcutaneous injection, with doses typically starting at 2.5 mg and gradually titrated upwards to a maintenance dose of 5 mg, 10 mg, or 15 mg, depending on individual response and tolerability. The Medicines and Healthcare products Regulatory Agency (MHRA) has approved Mounjaro for use in the UK, and the National Institute for Health and Care Excellence (NICE) has issued specific technology appraisals on its use within the NHS for type 2 diabetes (TA857).
As with any medication affecting metabolic pathways, tirzepatide can influence various hormonal systems in the body. Weight loss itself—regardless of the method—can have profound effects on hormone levels, including sex hormones such as testosterone. Understanding these potential changes is important for both patients and healthcare professionals managing treatment.
It's important to note that tirzepatide delays gastric emptying, which can reduce the absorption of oral medications, including oral contraceptives. Women using oral contraceptives may need additional contraceptive methods during treatment initiation and dose escalation.
Mounjaro® is the most innovative GLP-1 medication proven to dramatically curb appetite, hunger, and cravings to help professional men achieve substantial weight loss.
Start Here
Wegovy® is a weekly injectable GLP-1 medication with proven effectiveness in reducing appetite, hunger, and cravings to help busy professionals lose significant weight.
Start HereCurrent evidence suggests that weight loss achieved through tirzepatide treatment may influence testosterone levels, though the relationship is complex and differs between men and women. In clinical trials, significant weight reduction has been consistently observed with tirzepatide, and this metabolic improvement can have secondary effects on the endocrine system.
In men with obesity and type 2 diabetes, studies of weight loss interventions have shown that substantial weight reduction is often associated with increases in total testosterone levels. Obesity is linked to lower testosterone through several mechanisms: excess adipose tissue converts testosterone to oestradiol via the enzyme aromatase, and obesity-related inflammation and insulin resistance can suppress the hypothalamic-pituitary-gonadal axis. Additionally, obesity typically reduces sex hormone-binding globulin (SHBG) levels, which lowers total testosterone measurements. When men lose significant weight—whether through lifestyle modification, bariatric surgery, or pharmacotherapy—testosterone levels frequently rise towards the normal range, partly due to increased SHBG. While specific data on tirzepatide's effects on testosterone are still emerging, the hormone changes are likely mediated through these weight-loss mechanisms rather than direct drug effects.
In women, particularly those with polycystic ovary syndrome (PCOS), the picture is different. PCOS is characterised by elevated androgens (including testosterone), insulin resistance, and often obesity. Weight loss in women with PCOS—including that achieved with GLP-1 receptor agonists like liraglutide and semaglutide—has been associated with reductions in elevated testosterone levels and improvements in menstrual regularity and ovulation. This represents a normalisation of hormonal imbalance rather than a deficiency. While direct evidence for tirzepatide in PCOS is limited, similar effects might be expected based on its weight-reducing properties.
It is important to note that there is no established direct pharmacological link between tirzepatide and testosterone production. The observed changes appear to be mediated primarily through weight loss, improved insulin sensitivity, and reduced adiposity rather than a direct drug effect on gonadal or adrenal steroid synthesis. Further long-term studies are needed to fully characterise these hormonal changes and their clinical significance in patients taking tirzepatide for diabetes or weight management.
Not all patients taking Mounjaro will experience clinically significant changes in testosterone levels, and the likelihood and direction of change depend on several factors including baseline hormonal status, degree of weight loss, sex, and underlying metabolic conditions.
Men with obesity-related hypogonadism are most likely to see increases in testosterone. This condition, sometimes called functional hypogonadism, is characterised by low or low-normal testosterone levels in the context of obesity, metabolic syndrome, or type 2 diabetes. These men may notice improvements in symptoms such as low energy, reduced libido, or mood changes as their testosterone levels rise with weight loss. However, it is important to distinguish this from primary hypogonadism (testicular failure) or secondary hypogonadism due to pituitary disorders, which would not be expected to improve with weight loss alone.
Women with PCOS or hyperandrogenism may experience beneficial reductions in elevated testosterone levels. These women often present with symptoms such as irregular periods, hirsutism (excess facial or body hair), acne, and difficulty conceiving. Weight loss achieved through tirzepatide may help normalise androgen levels and improve these symptoms. Additionally, the restoration of more regular ovulation means that women of childbearing potential should be counselled about contraception, as fertility may improve during treatment.
Importantly, tirzepatide can reduce the effectiveness of oral contraceptives. Women using oral contraceptives should use additional barrier contraception for 4 weeks after starting tirzepatide and for 4 weeks after each dose increase, or consider non-oral contraceptive methods. Tirzepatide should be discontinued at least 1 month before planned pregnancy and is not recommended during pregnancy or breastfeeding.
Patients with minimal weight loss or those already at a healthy weight (if prescribed for diabetes management alone) are less likely to experience significant testosterone changes. The magnitude of hormonal change generally correlates with the degree of weight loss and metabolic improvement achieved.
Older adults and those with multiple comorbidities should be monitored carefully, as hormonal changes may interact with other medications or conditions. Any patient experiencing symptoms suggestive of hormonal imbalance—whether high or low testosterone—should discuss these with their GP or prescribing clinician.
Monitoring and communication with healthcare professionals are essential for managing potential hormonal changes during tirzepatide treatment. Before starting the medication, your doctor should take a comprehensive medical history, including any symptoms of hormonal imbalance, and may arrange baseline blood tests including HbA1c, lipid profile, liver and kidney function, and in some cases, hormone levels.
During treatment, regular follow-up appointments allow for assessment of treatment response, tolerability, and any emerging symptoms. If you experience new or worsening symptoms that could relate to testosterone changes—such as significant changes in libido, mood disturbances, menstrual irregularities, or signs of virilisation in women—inform your healthcare provider promptly. Blood tests to measure testosterone and other relevant hormones can be arranged if clinically indicated.
For men experiencing symptoms of low testosterone that do not improve with weight loss, further investigation may be warranted. Your GP may check early morning testosterone levels on two separate occasions (as levels are typically highest in the morning), along with luteinising hormone (LH), follicle-stimulating hormone (FSH), sex hormone-binding globulin (SHBG), prolactin, and thyroid function tests. If persistent hypogonadism is confirmed despite metabolic improvement, referral to an endocrinologist may be appropriate, particularly if testosterone is consistently low with low or normal gonadotropins (LH/FSH), or if there are symptoms suggesting pituitary dysfunction.
For women with PCOS or irregular cycles, improvements in hormonal balance may restore fertility. It is crucial to use effective contraception if pregnancy is not desired, as tirzepatide is not recommended during pregnancy. Women using oral contraceptives should use additional barrier contraception for 4 weeks after starting tirzepatide and for 4 weeks after each dose increase. If you are planning pregnancy, discuss this with your doctor well in advance, as tirzepatide should be discontinued at least 1 month before attempting conception.
Lifestyle factors continue to play an important role in hormonal health. Regular physical activity, adequate sleep, stress management, and a balanced diet all support healthy testosterone levels and overall endocrine function. Avoiding excessive alcohol consumption and maintaining a healthy weight are particularly important.
When to seek urgent advice: Contact your healthcare provider immediately if you experience severe, persistent abdominal pain (which could indicate pancreatitis), symptoms of gallbladder disease, or signs of dehydration during gastrointestinal side effects. Patients taking tirzepatide with insulin or sulfonylureas should be vigilant for hypoglycaemia symptoms. Contact your GP promptly if you experience severe mood changes, signs of depression, significant changes in sexual function, or any symptoms causing concern. Women should seek medical attention for unexpected vaginal bleeding or signs of pregnancy.
If you suspect you are experiencing side effects from tirzepatide, you can report these through the MHRA Yellow Card scheme. Your healthcare team can provide personalised advice based on your individual circumstances and treatment goals.
Mounjaro (tirzepatide) does not directly affect testosterone production. Any changes in testosterone levels are primarily due to weight loss and improved metabolic health rather than a direct drug effect on hormone synthesis.
Men with obesity-related hypogonadism may experience increases in testosterone levels as they lose weight on Mounjaro. However, men with primary testicular failure or pituitary disorders would not be expected to see improvements from weight loss alone and may require specialist endocrine assessment.
Women with polycystic ovary syndrome or elevated androgens may experience beneficial reductions in testosterone with weight loss on Mounjaro, potentially improving symptoms such as irregular periods and hirsutism. Women of childbearing potential should use effective contraception, as fertility may improve and tirzepatide can reduce oral contraceptive effectiveness.
All medical content on this blog is created based on reputable, evidence-based sources and reviewed regularly for accuracy and relevance. While we strive to keep content up to date with the latest research and clinical guidelines, it is intended for general informational purposes only.
DisclaimerThis content is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional with any medical questions or concerns. Use of the information is at your own risk, and we are not responsible for any consequences resulting from its use.
