Can adding testosterone to a male during puberty add to size of penis?

1. Why researchers focus on deficiency and micropenis rather than typical puberty—medical studies explain the target group

Clinical studies repeatedly show that the most robust penile growth response to testosterone occurs in boys who start with clinically small penises or hormonal deficiencies, not in otherwise healthy adolescents. Pediatric endocrinology reports document cases where early or pubertal-era testosterone replacement in congenital hypogonadotropic hypogonadism or idiopathic micropenis raised adult penile length into the normal range, with some series reporting post-treatment adult length within two standard deviations of the mean ^{[1] [2]}. These interventions aim to replace missing androgen exposure that normally occurs in utero and at puberty; therefore, the effect is correction of a deficiency rather than augmentation beyond typical developmental outcomes ^{[5] [4]}.

2. Evidence that adding testosterone in normal puberty has limited or inconsistent impact

Population and fertility-focused studies find only weak or inconsistent correlations between adult circulating testosterone and penile length, implying that simply increasing testosterone during or after normal puberty does not guarantee larger adult size. Research comparing infertile and fertile men found no significant differences in adult testosterone levels and only weak associations with stretched penile length, which argues against a straightforward dose–response effect of extra testosterone on penile dimensions in men with typical development ^[3]. Gender-affirming care literature and some transmasculine studies report modest clitorophallus enlargement with exogenous androgens—about up to 2 cm in some series—but those findings come from different anatomical contexts and patient populations, limiting direct application to natal males undergoing typical puberty ^[6].

3. Timing matters: earlier treatment yields bigger effects in deficient cases

Studies focused on pediatric hormonal therapy emphasize the critical role of timing: testosterone given in infancy or across childhood can stimulate growth trajectories that approximate normal adult size for patients with congenital hormonal deficits. In micropenis cohorts treated in childhood or adolescence, measured increases in penile length were substantial—for example, some reports show increases from mean lengths of roughly 15–26 mm before treatment to 37–64 mm after therapy—highlighting that hormonal replacement during developmental windows restores growth that would otherwise be blunted ^{[2] [1]}. The restorative principle underpins current clinical practice: treat deficiencies early to reach expected adult outcomes rather than attempting augmentation after growth windows close ^[5].

4. Combination therapies and animal models suggest complexity beyond testosterone alone

Preclinical and combined-treatment studies show complex interactions between growth hormone axes and androgens. Rat models of micropenis treated with combined growth hormone and testosterone achieved normalization of penile dimensions more reliably than single-agent therapy, suggesting that growth hormone signaling modulates androgenic effects on genital tissues ^[7]. Human pediatric data also note that growth hormone therapy in growth hormone–deficient boys can improve penile and testicular metrics, indicating that androgen-driven genital growth depends on broader endocrine milieu and tissue responsiveness, not just circulating testosterone levels ^{[8] [7]}.

5. What this means for clinicians, parents, and adolescents weighing testosterone use

The scientific literature supports testosterone therapy when a medical diagnosis of testosterone deficiency or micropenis exists, with documented benefit if timed during development ^{[1] [2]}. For adolescents without such diagnoses, the evidence does not support using exogenous testosterone to reliably increase penile size and raises concerns about inappropriate use, variable efficacy, and potential side effects; clinical guidelines emphasize evaluation for underlying endocrine disorders before any hormone treatment ^{[3] [4]}. Researchers and clinicians also note that data from transgender care and surgical-prep contexts show some tissue enlargement with androgens, but those findings reflect different goals and anatomical responses and should not be extrapolated without caution ^{[6] [4]}.