Finasteride Young Adult (18 to 29) Monitoring: Lab Schedule, Side-Effect Tracking, and When to Stop

Does finasteride 1 mg need routine lab work?

Of the lab values, the Propecia label discusses PSA directly, and it reports the hormone shift rather than a monitoring target [1]. In the clinical studies of 1 mg in men aged 18 to 41, mean serum PSA fell from 0.7 ng/mL at baseline to 0.5 ng/mL at month 12 [1]. The label states that any confirmed increase from the lowest PSA value while on Propecia may signal prostate cancer and should be evaluated, even if the value is still within the normal range for men not taking a 5-alpha reductase inhibitor, and that non-compliance with therapy may also affect PSA results [1]. Mean circulating testosterone and estradiol rise by about 15% and remain within the physiologic range, and finasteride has no affinity for the androgen receptor [1].

The often-quoted 50% fall and the rule of doubling a PSA belong to the 5 mg Proscar label, which reports a fall of approximately 50% within six months of treatment and tells clinicians to double an isolated PSA value in men who have taken it for six months or more [4]. That is a different product and dose from the hair-loss tablet.

Finasteride 1 mg is a prescription tablet taken once daily with or without food [5][1].

What the trials counted

Three controlled trials of 12 months enrolled 945 men on finasteride 1 mg and 934 on placebo, all between 18 and 41 years old [1]. Drug-related decreased libido was reported by 1.8% versus 1.3%, erectile dysfunction by 1.3% versus 0.7%, and ejaculation disorder by 1.2% versus 0.7%; 3.8% versus 2.1% reported at least one of these (p=0.04), and 1.2% versus 0.9% stopped the drug for a sexual adverse event [1]. Each individual rate fell to 0.3% or lower by the fifth year of treatment [1]. A self-administered sexual function questionnaire at month 12 favored placebo in three of four domains — sexual interest, erections and perception of sexual problems — with no significant difference in overall satisfaction with sex life [1].

A 2019 meta-analysis of 15 randomized placebo-controlled trials (4,495 men treated for androgenetic alopecia) found a relative risk of sexual dysfunction of 1.57 (95% CI 1.19 to 2.08) for finasteride 1 mg or dutasteride 0.5 mg, and 1.66 (95% CI 1.20 to 2.30) for finasteride alone [6]. A separate review of 34 finasteride trials for hair loss found that none had adequate safety reporting, 76% assessed safety for a year or less, and funnel plots suggested under-detection of sexual adverse effects [7].

Sexual side effects that continue after stopping

The Propecia label's postmarketing section lists sexual dysfunction that continued after discontinuation of treatment, including erectile dysfunction, libido disorders, ejaculation disorders and orgasm disorders, plus male infertility and poor seminal quality, with normalization or improvement in seminal quality reported after stopping [1]. The label states that these are voluntary reports from a population of uncertain size and that a causal relationship cannot reliably be established [1].

Two studies are usually cited here, and both have limits. Interviews with 71 otherwise healthy men aged 21 to 46 who reported new sexual dysfunction lasting at least three months after stopping found mean finasteride use of 28 months and mean persistence of 40 months; the men were self-selected and reporting from memory, so the study cannot show how often this happens or why [8]. A medical-record study of 11,909 men exposed to finasteride or dutasteride found persistent erectile dysfunction, defined as lasting 90 days or more after stopping and treated with a PDE5 inhibitor, in 167 men (1.4%), with median persistence of 1,348 days [9].

Mood and suicidal thoughts

Finasteride has no boxed warning for depression, suicidal ideation or sexual dysfunction [1]. The labeling history: the Propecia label of June 2021 listed postmarketing depression, and on May 31, 2022 the FDA sent a safety labeling change order citing new information on suicidal ideation and behavior plus additional sexual dysfunction and psychoneurocognitive events; the supplement approved August 1, 2022 changed the wording to depression, suicidal ideation and behavior [2].

A 2021 analysis of VigiBase, the WHO global database of individual case safety reports, found 356 reports of suicidality and 2,926 reports of psychological adverse events among finasteride users, with a reporting odds ratio of 1.63 (95% CI 1.47 to 1.81) for suicidality and 4.33 (95% CI 4.17 to 4.49) for psychological adverse events; the signal was stronger in patients aged 45 or younger (odds ratio 3.47) and in those taking it for alopecia (2.06) [10]. Spontaneous reporting databases detect signals, not causes.

Two large cohorts looked at harder outcomes, and both studied older men using 5-alpha reductase inhibitors, largely for prostate enlargement; their results do not directly describe men in their twenties taking finasteride 1 mg [11][12]. In 93,197 Ontario men aged 66 or older, suicide risk was not raised (hazard ratio 0.88, 95% CI 0.53 to 1.45), while self-harm was higher in the first 18 months (1.88, 95% CI 1.34 to 2.64) and depression was higher both early (1.94, 95% CI 1.73 to 2.16) and later (1.22, 95% CI 1.08 to 1.37) [11]. In 2,236,876 Swedish men aged 50 to 90, of whom 70,645 started finasteride at a median age of 73, depression was more common (hazard ratio 1.61, 95% CI 1.48 to 1.75) and suicide was not significantly associated (1.22, 95% CI 0.99 to 1.49) [12].

A small cross-sectional study compared 61 former users who had persistent sexual side effects with 29 men who had hair loss and had never used finasteride: depressive symptoms on the Beck Depression Inventory II (score of 14 or more) were present in 75% versus 10% (P<0.0001), in a self-selected sample that cannot establish cause [13].

Fertility and semen

On 1 mg, the label reports a median ejaculate volume change of -0.3 mL (-11%) versus -0.2 mL (-8%) on placebo at 48 weeks [1]. A double-blind trial enrolled 181 men aged 19 to 41, with a subset of 79 providing sequential semen samples: after 48 weeks of 1 mg daily there was no significant effect on sperm concentration, total sperm per ejaculate, motility or morphology, and the difference in ejaculate-volume change from placebo was small and not statistically significant [15]. In that trial the small changes in prostate volume and PSA reversed after the drug was stopped [15]. The 5 mg Proscar label — again, a different product and dose — reports no clinically meaningful effect on sperm concentration, motility, morphology or pH after 24 weeks, a median ejaculate volume fall of 0.6 mL (22.1%) with a reduction in total sperm per ejaculate, and reversal with an average of 84 weeks to return to baseline [4].

In a fertility-clinic series, 27 of 4,400 men presenting for evaluation were taking finasteride (mean duration 57.4 months, mean dose 1.04 mg/day); after discontinuation sperm counts rose an average of 11.6-fold, 57% of men with severe oligospermia rose above 15 million/mL, and no man's count fell [3]. That is a selected infertility population, not a sample of healthy men in their twenties.

What the label says about stopping

The Propecia label records what has been reported and gives no score or lab value that defines when to stop. Its postmarketing list includes the persistent sexual effects described above, depression and suicidal ideation and behavior, male breast cancer (relationship to long-term use unknown), hypersensitivity reactions such as rash, itching, hives and angioedema, testicular pain, blood in the semen, and breast tenderness and enlargement [1][2]. It also reports the other direction: resolution of sexual adverse events occurred in men who discontinued therapy for them and in most of those who continued [1].

Stopping has a predictable hair consequence. Daily use for three months or more is usually needed before benefit is seen, continued use is needed to sustain benefit, and withdrawal leads to reversal of effect within 12 months [1].