Testosterone replacement therapy (TRT) and obstructive sleep apnoea (OSA) share a complex, bidirectional relationship that requires careful clinical consideration. Untreated sleep apnoea can suppress testosterone production through sleep disruption and intermittent hypoxia, whilst testosterone therapy may potentially worsen sleep apnoea through effects on respiratory drive, upper airway function, and fluid distribution. Not all men receiving testosterone will develop or experience worsening OSA, but healthcare professionals should maintain vigilance, particularly in those with risk factors such as obesity or increased neck circumference. Pre-treatment screening and ongoing monitoring are essential to balance the benefits of testosterone replacement against potential respiratory risks.

Understanding the Link Between Testosterone and Sleep Apnoea

Testosterone replacement therapy (TRT) and obstructive sleep apnoea (OSA) share a complex, bidirectional relationship that clinicians and patients must carefully consider. Sleep apnoea is a condition characterised by repeated episodes of partial or complete upper airway obstruction during sleep, leading to oxygen desaturation, sleep fragmentation, and daytime symptoms such as excessive sleepiness and impaired concentration.

Interestingly, untreated sleep apnoea can itself lower testosterone levels. The sleep disruption and intermittent hypoxia associated with OSA may suppress the hypothalamic-pituitary-gonadal axis, reducing endogenous testosterone production. Men with moderate to severe OSA often present with lower serum testosterone concentrations compared to those without sleep-disordered breathing. This typically represents functional (secondary/hypogonadotrophic) hypogonadism, and CPAP treatment may improve but not always fully normalise testosterone levels.

Conversely, testosterone therapy may influence sleep apnoea through several mechanisms. Testosterone can affect central respiratory drive, upper airway muscle tone, and fluid distribution in the neck tissues. Additionally, testosterone may alter sleep architecture and increase the frequency or severity of apnoeic episodes in susceptible individuals. The relationship is not straightforward, and individual responses vary considerably.

It is essential to recognise that not all men on testosterone therapy will develop or experience worsening sleep apnoea. However, the potential association means that healthcare professionals should maintain a high index of suspicion, particularly in men with risk factors such as obesity, increased neck circumference, or a history of snoring.

Diagnosis of hypogonadism requires two separate morning testosterone measurements and assessment of clinical features, as outlined in NICE Clinical Knowledge Summaries. If OSA is suspected, referral to an NHS sleep service is appropriate before confirming the need for testosterone therapy.

How Testosterone Treatment May Worsen Sleep Apnoea

Testosterone replacement therapy can potentially exacerbate obstructive sleep apnoea through several physiological mechanisms, though the evidence base remains evolving and somewhat inconsistent. The Medicines and Healthcare products Regulatory Agency (MHRA) and product literature for testosterone preparations include sleep apnoea as a warning/precaution rather than a formal contraindication, advising caution in men at risk.

One proposed mechanism involves changes in upper airway anatomy and function. Testosterone may promote fluid retention and potentially affect upper airway tissues, though evidence for direct effects on pharyngeal soft tissue mass is limited. This theoretical risk may be more significant in men who are overweight or obese, where baseline airway compromise already exists. While testosterone therapy typically reduces overall fat mass and improves body composition, any fluid retention effects could potentially influence upper airway dynamics.

Testosterone may also affect central respiratory control. Some research suggests that androgens might influence ventilatory drive during sleep, particularly during rapid eye movement (REM) sleep when muscle tone is naturally reduced. This could theoretically increase the frequency and duration of apnoeic events, though individual responses vary considerably.

Erythrocytosis (increased red blood cell production) is a recognised side effect of testosterone therapy. While this primarily raises concerns about cardiovascular risk, the resultant increase in blood viscosity may theoretically worsen the physiological consequences of intermittent hypoxia during apnoeic episodes. UK product information recommends monitoring haematocrit and reducing or withholding testosterone if levels exceed 0.54.

It is important to note that the clinical significance of these effects varies considerably between individuals. Some men may experience no change in their sleep apnoea status, whilst others may develop new-onset OSA or see existing disease worsen. Patient-specific factors—including baseline OSA severity, body mass index (BMI), age, and testosterone dose—all influence outcomes.

Sleep Apnoea Screening Before Starting Testosterone Therapy

Comprehensive pre-treatment assessment is essential to identify men at risk of sleep apnoea before initiating testosterone replacement therapy. NICE Clinical Knowledge Summaries on hypogonadism emphasise the importance of evaluating cardiovascular and respiratory risk factors, though specific sleep apnoea screening protocols are not universally mandated.

Clinical history should include targeted questions about sleep-related symptoms:

• Loud, habitual snoring (particularly if witnessed by a partner)

• Observed apnoeic episodes or gasping during sleep

• Excessive daytime sleepiness or unrefreshing sleep

• Morning headaches

• Difficulty concentrating or memory problems

• Nocturia (frequent nighttime urination)

Physical examination should assess key risk factors including BMI, neck circumference (>40 cm in men is associated with increased OSA risk), and signs of upper airway narrowing such as enlarged tonsils or a crowded oropharynx (Mallampati score). Blood pressure measurement is important, as hypertension—particularly treatment-resistant hypertension—is strongly associated with OSA.

Validated screening questionnaires such as the Epworth Sleepiness Scale or STOP-BANG questionnaire can help stratify risk. The STOP-BANG tool assesses eight factors: Snoring, Tiredness, Observed apnoea, high blood Pressure, BMI >35 kg/m², Age >50 years, Neck circumference >40 cm, and male Gender. A score of ≥3 suggests moderate to high OSA risk.

Men identified as high-risk should undergo formal sleep assessment before starting testosterone therapy. This typically involves referral to a sleep clinic for diagnostic testing, which may include home-based limited-channel studies or in-laboratory polysomnography, depending on local pathways and clinical suspicion. The apnoea-hypopnoea index (AHI)—the number of apnoeic and hypopnoeic events per hour of sleep—determines OSA severity: mild (5–14 events/hour), moderate (15–29 events/hour), or severe (≥30 events/hour).

Treating existing sleep apnoea before initiating testosterone therapy is generally advisable, as this may improve endogenous testosterone levels and clarify whether testosterone replacement is truly necessary.

Importantly, people with excessive daytime sleepiness should not drive and may need to inform the DVLA if diagnosed with OSA/OSAHS, particularly if it affects their alertness when driving.

Managing Sleep Apnoea During Testosterone Treatment

For men with known sleep apnoea who require testosterone therapy, or those who develop OSA during treatment, integrated management strategies are essential to optimise both conditions safely. The approach should be individualised, balancing the benefits of testosterone replacement against the potential respiratory risks.

Continuous positive airway pressure (CPAP) therapy remains the gold-standard treatment for moderate to severe obstructive sleep apnoea. CPAP delivers pressurised air through a mask, maintaining upper airway patency throughout the sleep cycle. Men with OSA who are prescribed testosterone should be established on effective CPAP therapy, with regular monitoring of adherence and efficacy. Good CPAP compliance (typically defined as ≥4 hours per night on ≥70% of nights) is crucial for symptom control and reducing cardiovascular risk.

For mild to moderate OSA where CPAP is not tolerated, mandibular advancement devices (MAD) may be an alternative option, as recommended by NICE guidance.

Lifestyle modifications play a vital supporting role:

• Weight reduction: Even modest weight loss (5–10% of body weight) can significantly improve OSA severity

• Alcohol avoidance: Particularly in the evening, as alcohol relaxes upper airway muscles

• Sleep position: Avoiding supine sleep can reduce apnoea frequency in position-dependent OSA

• Smoking cessation: Reduces upper airway inflammation and fluid retention

Testosterone dosing and formulation may require adjustment. If sleep apnoea worsens after starting TRT, clinicians might consider reducing the dose, switching to a different preparation, or temporarily discontinuing therapy whilst OSA is optimised. While evidence for specific formulation choices in OSA risk mitigation is limited, individualised decisions based on serum level profiles and tolerability are appropriate.

Regular monitoring is essential and should include:

• Periodic reassessment of sleep symptoms and daytime functioning

• Review of CPAP adherence data (if applicable)

• Monitoring of haematocrit levels (consider dose reduction or withholding TRT if haematocrit >0.54)

• Cardiovascular risk factor assessment

Some men may benefit from repeat sleep studies during testosterone therapy to objectively assess any changes in OSA severity, particularly if symptoms worsen or new concerns arise.

When to Seek Medical Advice About Testosterone and Sleep Issues

Patients receiving testosterone replacement therapy should be aware of warning signs that warrant prompt medical review. Early recognition of sleep-related problems can prevent serious complications and allow timely intervention.

Contact your GP or prescribing clinician if you experience:

• New or worsening snoring, particularly if your partner reports that you stop breathing during sleep

• Excessive daytime sleepiness that interferes with daily activities or creates safety concerns

• Morning headaches or waking feeling unrefreshed despite adequate time in bed

• Difficulty concentrating, memory problems, or mood changes that develop after starting testosterone

• Witnessed apnoeic episodes (breathing pauses during sleep)

• Unexplained weight gain or increasing neck size

Seek urgent medical attention (call 999 or attend A&E) if you develop:

• Severe, persistent headaches

• Chest pain or palpitations

• Sudden shortness of breath

• Confusion or significant cognitive impairment

• Signs of stroke (facial drooping, arm weakness, speech difficulty)

These symptoms may indicate serious complications such as severe oxygen desaturation, cardiovascular events, or erythrocytosis-related thrombosis.

Before starting testosterone therapy, discuss your sleep quality and any history of snoring or sleep problems with your healthcare provider. If you have been diagnosed with sleep apnoea, ensure your prescriber is aware, as this may influence treatment decisions. Men with severe, untreated sleep apnoea should generally not start testosterone therapy until their OSA is adequately managed.

Regular follow-up appointments are essential for all men on testosterone replacement. These typically occur at 3 months, 6 months, and 12 months, then annually, but may be more frequent if sleep concerns arise. During these reviews, be honest about any sleep-related symptoms, even if they seem minor.

If you are using CPAP therapy, maintain good adherence and report any problems with your equipment or mask fit. Your sleep clinic should provide ongoing support, but your testosterone prescriber should also be kept informed of your OSA management status.

Important driving advice: Do not drive if you feel sleepy. If diagnosed with obstructive sleep apnoea syndrome (OSAS) that causes excessive sleepiness affecting your driving, you must inform the DVLA.

If you suspect you've experienced a side effect from testosterone treatment, you can report it through the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk or the Yellow Card app).

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