Many men considering treatment for male pattern baldness worry whether hair loss medications will lower their testosterone levels. This concern is particularly common regarding finasteride, the most widely prescribed oral treatment in the UK. Whilst finasteride does affect hormone metabolism by blocking the conversion of testosterone to dihydrotestosterone (DHT), clinical evidence consistently demonstrates that testosterone levels typically remain within normal ranges or may even increase slightly. Understanding how different hair loss treatments interact—or don't interact—with testosterone is essential for making informed decisions about managing androgenetic alopecia whilst maintaining overall hormonal health.

How Hair Loss Treatments Affect Testosterone Levels

Many individuals considering treatment for male pattern baldness (androgenetic alopecia) express concern about potential effects on testosterone levels. This concern is understandable, given that the most effective pharmacological treatments target hormones involved in hair loss. However, it is important to distinguish between different types of hormonal effects and understand what current evidence demonstrates.

The most commonly prescribed oral medication for male pattern hair loss in the UK is finasteride, which works by inhibiting an enzyme called 5-alpha reductase. This enzyme converts testosterone into dihydrotestosterone (DHT), a more potent androgen responsible for miniaturising hair follicles in genetically susceptible individuals. Whilst finasteride reduces DHT levels by approximately 70%, clinical studies consistently show that serum testosterone levels typically remain within the normal range or may even increase slightly due to reduced conversion to DHT.

Other hair loss treatments, such as minoxidil (a topical medication), do not interact with testosterone or DHT pathways at all. Minoxidil works primarily through potassium channel opening and prolonging the growth phase of hair follicles (anagen phase). Low-level laser therapy, platelet-rich plasma (PRP) injections, and hair transplantation similarly have no direct impact on testosterone metabolism.

Understanding the specific mechanism of each treatment is essential for making informed decisions. Whilst finasteride does alter androgen metabolism, the effect is targeted at DHT rather than testosterone itself, and for most men, this distinction is clinically significant in terms of both efficacy and side effect profile.

Finasteride and DHT: Understanding the Mechanism

Finasteride is a type II 5-alpha reductase inhibitor licensed by the MHRA for treating male pattern baldness at a 1mg daily dose (marketed as Propecia). The drug's mechanism is highly specific: it blocks the enzyme responsible for converting testosterone into DHT, particularly in hair follicles and the prostate gland. This targeted action is what makes finasteride effective for both hair loss and benign prostatic hyperplasia (at higher doses).

DHT is approximately five times more potent than testosterone at binding to androgen receptors. In individuals with genetic susceptibility to androgenetic alopecia, DHT binds to receptors in scalp hair follicles, causing progressive miniaturisation—the follicles become smaller and produce finer, shorter hairs until eventually ceasing to produce visible hair. By reducing DHT levels by approximately 60-70%, finasteride slows or halts this miniaturisation process in many men, and in some cases, promotes partial regrowth of hair.

Crucially, because finasteride blocks the conversion pathway, testosterone that would normally be converted to DHT remains as testosterone or may be converted to oestradiol via aromatase. According to clinical data in the product information, whilst DHT levels drop significantly, total serum testosterone levels either remain stable or increase by approximately 10-15% on average. This increase is generally not clinically significant and remains within normal physiological ranges, as does any change in oestradiol levels.

Finasteride selectively inhibits the type II 5-alpha reductase enzyme (predominantly found in hair follicles and prostate) rather than type I (found more widely in skin and liver). Dutasteride, which inhibits both enzyme types, is not licensed in the UK for treating hair loss.

Does Lowering DHT Mean Lower Testosterone?

A common misconception is that reducing DHT automatically means reducing testosterone. In reality, these are distinct hormones with different roles, and lowering one does not necessarily lower the other. Testosterone is the primary male sex hormone produced by the testes, responsible for maintaining muscle mass, bone density, libido, mood, and numerous other physiological functions. DHT, whilst derived from testosterone, has more specific roles, particularly in the development of male characteristics during puberty and in maintaining prostate function.

When finasteride blocks the conversion of testosterone to DHT, the testosterone that would have been converted remains in circulation. Studies measuring hormone levels in men taking finasteride consistently show that serum testosterone levels do not decrease—in fact, they often show a modest increase. Clinical studies referenced in the product information show that men taking 1mg finasteride daily experienced an average increase in serum testosterone, whilst DHT levels decreased by approximately 70%.

This biochemical reality is important for understanding potential side effects. Symptoms such as reduced libido or erectile dysfunction, which occur in a small percentage of men taking finasteride (reported in approximately 1-2% of users in clinical trials), are not due to low testosterone levels. Instead, these effects may relate to reduced DHT activity at androgen receptors or, in some cases, may be multifactorial.

For men concerned about testosterone levels, routine blood tests can provide reassurance. Routine testosterone monitoring is not required according to the product information unless specific symptoms suggest hypogonadism, as the medication does not typically cause clinically significant changes to testosterone levels. If sexual side effects occur, they should be discussed with a GP, but low testosterone is rarely the underlying cause in men taking standard-dose finasteride for hair loss.

Importantly, if you experience depression or suicidal thoughts while taking finasteride, you should stop taking the medication and seek medical advice immediately.

Potential Hormonal Side Effects of Hair Loss Medications

Whilst finasteride does not lower testosterone, it can produce other hormonal effects that warrant consideration. According to the product information, the most commonly reported side effects relate to sexual function, including reduced libido (affecting approximately 1.8% of men in clinical trials), erectile dysfunction (1.3%), and ejaculatory disorders (1.2%). These rates are only slightly higher than placebo groups, and for most men who experience these effects, they resolve either with continued treatment or upon discontinuation.

The MHRA has highlighted that some men report persistent sexual side effects even after stopping finasteride. Regulatory bodies including the MHRA and EMA have updated product information to acknowledge reports of persistent sexual dysfunction. Current evidence suggests that if persistent effects occur, they are uncommon, but patients should be aware of this possibility.

Other potential hormonal effects include gynaecomastia (breast tissue enlargement), reported in less than 1% of users. There have been rare reports of male breast cancer in men using finasteride. The MHRA has also identified mood changes, including depression and anxiety, as potential side effects. If you experience depression or suicidal thoughts while taking finasteride, you should stop taking the medication and seek medical advice immediately.

Important safety considerations include:

• Finasteride is contraindicated in women of childbearing potential due to risk of feminisation of male foetuses

• Pregnant women should not handle crushed or broken finasteride tablets due to potential risks to male foetuses

• Men taking finasteride should not donate blood until at least one month after stopping treatment

• Any breast changes, lumps, or nipple discharge should be reported to a GP promptly

• Persistent sexual dysfunction or mood changes warrant medical review

Minoxidil, by contrast, has no hormonal effects but can cause scalp irritation, unwanted hair growth (if solution runs onto other areas), and rarely, cardiovascular effects such as palpitations or dizziness. Side effects vary by formulation and concentration.

You can report any suspected side effects to the MHRA through the Yellow Card Scheme (yellowcard.mhra.gov.uk).

Monitoring Testosterone During Hair Loss Treatment

For most men using finasteride or other hair loss treatments, routine testosterone monitoring is not clinically necessary. According to the product information, regular hormone testing is not required for men on standard-dose finasteride (1mg daily) for androgenetic alopecia, as the medication does not typically cause testosterone deficiency. However, there are specific circumstances where monitoring may be appropriate.

Men who develop symptoms potentially suggestive of hypogonadism—such as persistent fatigue, reduced libido, erectile dysfunction, loss of muscle mass, mood disturbance, or reduced bone density—should discuss these with their GP. In such cases, a morning serum testosterone level (ideally taken between 8-10am when levels are highest) may be measured. If levels are low, repeat testing is typically performed to confirm the finding, as testosterone levels can fluctuate.

It is worth noting that symptoms attributed to finasteride may have alternative explanations. Erectile dysfunction, for instance, is common in the general population and increases with age, cardiovascular risk factors, diabetes, psychological stress, and relationship issues. Similarly, fatigue and mood changes have numerous potential causes. A thorough clinical assessment is essential to avoid incorrectly attributing symptoms to hair loss medication.

When to contact your GP:

• Depression or suicidal thoughts (stop finasteride immediately and seek medical advice)

• Persistent sexual dysfunction that concerns you or affects quality of life

• Breast lumps, pain, or nipple discharge

• Significant mood changes, depression, or anxiety

• Symptoms of allergic reaction (rash, swelling, difficulty breathing) – seek emergency care for severe reactions

• Any other side effects that are severe or persistent

For men using minoxidil, monitoring focuses on treatment response and tolerability rather than hormonal effects. Photographic documentation every 3-6 months can help assess efficacy objectively. If cardiovascular symptoms such as chest pain, rapid heartbeat, or significant dizziness occur, medical advice should be sought promptly, although such effects are uncommon with topical application.

Alternative Hair Loss Options Without Hormonal Effects

For individuals concerned about hormonal treatments or those who experience side effects from finasteride, several alternative approaches exist, though their efficacy varies. Minoxidil remains the primary non-hormonal pharmacological option and is available over the counter in the UK in 2% and 5% formulations. Applied topically according to the specific product instructions (frequency varies by formulation), minoxidil can slow hair loss and promote regrowth in approximately 40-60% of users, though results are generally more modest than with finasteride, and continuous use is required to maintain benefits.

Low-level laser therapy (LLLT) devices, including laser combs and caps, have some evidence supporting their use for androgenetic alopecia. These devices emit red light that may stimulate hair follicles through increased cellular energy production. Whilst LLLT does not produce dramatic results, studies suggest modest improvements in hair density and thickness with consistent use over several months. The treatment is time-consuming (typically requiring 20-30 minutes several times weekly) and devices can be expensive, but there are no systemic side effects.

Platelet-rich plasma (PRP) therapy involves extracting a patient's blood, concentrating the platelets, and injecting the plasma into the scalp. Growth factors released from platelets may stimulate hair follicles. Evidence quality is variable, with some studies showing benefit and others showing minimal effect. PRP is not available on the NHS for hair loss and private treatment can be costly, typically requiring multiple sessions.

Other considerations include:

• Hair transplantation: Surgical redistribution of hair follicles from donor areas; permanent but expensive and invasive

• Cosmetic camouflage: Hair fibres, scalp micropigmentation, or hairpieces for immediate aesthetic improvement

• Nutritional optimisation: Ensuring adequate protein, iron, zinc, and biotin intake, though supplementation only helps if deficiency exists

• Addressing underlying causes: Treating thyroid disorders, iron deficiency, or other medical conditions contributing to hair loss

It is important to maintain realistic expectations with any hair loss treatment. Complete regrowth to pre-loss density is uncommon, and maintenance of existing hair is often the primary goal. Consulting a GP or dermatologist can help determine the most appropriate approach based on individual circumstances, hair loss pattern, and personal preferences regarding hormonal versus non-hormonal interventions.

Frequently Asked Questions