Testosterone is widely recognized as the primary male sex hormone, responsible for deepening voices, building muscle mass, and driving sperm production. Still, this reputation tells only half the story. Now, the biological reality is far more nuanced: the testes and ovaries both release the hormone testosterone, making it a critical chemical messenger for every human body, regardless of sex assigned at birth. Understanding this shared endocrine function dismantles outdated binaries and reveals why hormonal balance is a universal health concern That's the part that actually makes a difference..
The Shared Endocrine Origin
To understand why both gonads produce testosterone, we must look at embryonic development. In the early weeks of gestation, the gonads are "bipotential"—identical structures that have not yet differentiated into testes or ovaries. They possess the same cellular machinery capable of producing androgens (like testosterone) and estrogens Surprisingly effective..
Under the influence of specific genetic signals—primarily the SRY gene on the Y chromosome—the bipotential gonads differentiate into testes. Leydig cells within the testes then become high-volume testosterone factories. Which means in the absence of that signal, the gonads develop into ovaries. Crucially, the ovarian theca cells retain the enzymatic pathway to synthesize androgens, including testosterone. While the volume of production differs drastically—testes produce roughly 10 to 20 times more testosterone daily than ovaries—the qualitative ability to produce it is a shared evolutionary heritage.
Testosterone Production in the Testes
In individuals with testes, testosterone synthesis is the dominant gonadal activity. The process is tightly regulated by the hypothalamic-pituitary-gonadal (HPG) axis.
- The Hypothalamus releases Gonadotropin-Releasing Hormone (GnRH) in pulses.
- The Anterior Pituitary responds by secreting Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH).
- Leydig Cells in the testes possess LH receptors. When LH binds, it triggers a cascade converting cholesterol into pregnenolone, then through several intermediates (including DHEA and androstenedione) into testosterone.
This production is relatively constant in adulthood, though it follows a diurnal rhythm (highest in the morning) and declines gradually with age—often called andropause or late-onset hypogonadism. The testosterone produced here acts locally to support spermatogenesis within the seminiferous tubules and systemically to maintain libido, bone density, red blood cell production, and muscle mass.
The official docs gloss over this. That's a mistake And that's really what it comes down to..
Testosterone Production in the Ovaries
In individuals with ovaries, the hormonal landscape is cyclical rather than tonic. The ovarian steroidogenesis follows the "two-cell, two-gonadotropin" theory, where theca cells and granulosa cells cooperate.
- Theca Cells (Outer Layer): Stimulated by LH, these cells produce androgens—primarily androstenedione and testosterone. They lack the enzyme aromatase, so they cannot convert these androgens into estrogens.
- Granulosa Cells (Inner Layer): Stimulated by FSH, these cells take the androgens diffusing from theca cells and, using the enzyme aromatase, convert them into estradiol (the primary estrogen).
Which means, testosterone in the ovaries is primarily a precursor for estrogen synthesis. That said, a small but significant amount escapes conversion and enters the bloodstream. Levels fluctuate across the menstrual cycle: they rise slightly during the follicular phase, peak around ovulation (coinciding with the LH surge), and dip during the luteal phase. Post-menopause, ovarian testosterone production does not cease entirely; the ovarian stroma continues to produce androgens, often becoming the primary source of testosterone in older women after adrenal production (DHEA) also declines.
The Critical Role of the Adrenal Glands
While the gonads are the headline actors, the adrenal glands are the essential supporting cast. These are weak androgens that serve as circulating reservoirs. Here's the thing — both sexes produce Dehydroepiandrosterone (DHEA) and Androstenedione in the adrenal cortex (zona reticularis). Peripheral tissues—skin, fat, liver, brain, and breast tissue—possess the enzymes (like 17β-hydroxysteroid dehydrogenase) to convert these precursors into active testosterone or estrogen locally.
Worth pausing on this one.
This intracrinology (local hormone production) explains why testosterone exerts effects even when gonadal production is low. That's why for post-menopausal women and aging men, adrenal precursors become the dominant source of sex steroids. It also highlights why "total testosterone" blood tests only tell part of the story; tissue-level activity depends heavily on local enzyme expression.
Quick note before moving on.
Why Testosterone Matters Beyond Reproduction
The narrative that testosterone is "for men" and estrogen is "for women" is scientifically obsolete. Both hormones are present and functionally vital in all bodies.
In Bodies with Ovaries (Female Physiology)
- Libido and Sexual Function: Testosterone is a primary driver of sexual desire, arousal, and genital sensitivity in women. Low levels (common with oral contraceptives, which spike Sex Hormone Binding Globulin (SHBG) and lower free testosterone) are a leading cause of Hypoactive Sexual Desire Disorder (HSDD).
- Bone Health: Testosterone stimulates osteoblasts (bone-building cells) directly via androgen receptors and indirectly via aromatization to estrogen. This is key for achieving peak bone mass and preventing osteoporosis.
- Muscle Mass and Metabolism: It supports lean body mass maintenance and insulin sensitivity. Low testosterone in women correlates with increased visceral adiposity and metabolic syndrome risk.
- Cognitive Function and Mood: Androgen receptors exist throughout the brain, particularly in the hippocampus and amygdala. Optimal levels support verbal memory, spatial ability, and mood stability.
- Cardiovascular Health: The relationship is complex, but physiological levels appear vasoprotective, improving endothelial function and lipid profiles.
In Bodies with Testes (Male Physiology)
- Spermatogenesis: High intratesticular testosterone (100x serum levels) is non-negotiable for sperm production.
- Secondary Sexual Characteristics: Growth of facial/body hair, deepening of the voice, adam's apple development.
- Anabolic Effects: Protein synthesis, muscle hypertrophy, erythropoiesis (red blood cell production).
- Metabolic Regulation: Fat distribution (preventing visceral fat accumulation), glucose homeostasis.
The Concept of "Free" vs. "Total" Testosterone
Because the testes and ovaries both release the hormone testosterone into the bloodstream, but the binding proteins differ by sex and condition, measuring "Total Testosterone" can be misleading.
- SHBG (Sex Hormone Binding Globulin): Binds ~60% of testosterone with high affinity. Estrogen increases SHBG; insulin, androgens, and thyroid hormone decrease it. Women naturally have higher SHBG. Oral estrogen (birth control pills) skyrockets SHBG, rendering most testosterone biologically inactive.
- Albumin: Binds ~38% weakly.
- Free Testosterone: The remaining 1–2% is unbound and biologically active. It diffuses freely into cells.
Calculated Free Testosterone (cFT) or Bioavailable Testosterone (Free + Albumin-bound) are far superior clinical markers than Total Testosterone, especially when evaluating symptoms in women or men with metabolic syndrome/obesity (which lowers SHBG).
Clinical Implications: When Balance Goes Awry
Recognizing that both gonads produce testosterone changes how we diagnose and treat endocrine disorders.
High Testosterone in Ovarian Bodies (Hyperandrogenism)
The most common cause is Polycystic Ovary Syndrome (PCOS). Here, theca cells are hyper-responsive to LH (often elevated) and insulin (which acts as a co-gonadotropin), pumping out excess testosterone. Symptoms include hirsutism (male-pattern hair growth
, irregular menstrual cycles, and polycystic ovaries visible on ultrasound. Beyond reproductive concerns, hyperandrogenism in PCOS significantly increases the risk of insulin resistance, type 2 diabetes, and cardiovascular disease. PCOS affects approximately 6–12% of reproductive-aged women, making it one of the most prevalent hormonal disorders. The chronic elevation of androgens also impacts mental health, with higher rates of anxiety and depression observed in affected individuals.
Other causes of ovarian hyperandrogenism include ovarian tumors (functional or malignant) and, less commonly, congenital adrenal hyperplasia (CAH) due to enzyme deficiencies like 21-hydroxylase deficiency. In these cases, androgen levels may be markedly elevated, and diagnostic workup often involves imaging studies and specialized hormone assessments.
Low Testosterone in Ovarian Bodies (Hypoandrogenism)
While often overlooked, low androgen levels in women can lead to diminished sexual desire, fatigue, and reduced quality of life. Hypoandrogenism may result from menopause, surgical removal of ovaries, or suppression of the hypothalamic-pituitary-ovarian axis due to chronic stress, excessive exercise, or eating disorders. Some women experience persistent symptoms despite adequate estrogen replacement therapy, suggesting an independent role for androgens in female well-being.
In such cases, measuring free or bioavailable testosterone becomes crucial, as total levels may appear normal due to fluctuations in SHBG. Treatment options include low-dose transdermal testosterone preparations, which have shown efficacy in improving libido and overall sexual health without significant virilizing effects when monitored appropriately That alone is useful..
High Testosterone in Testicular Bodies (Pathological States)
In males, supraphysiologic testosterone levels typically arise from external sources, such as anabolic-androgenic steroid (AAS) abuse. Exogenous testosterone suppresses natural gonadotropin-releasing hormone (GnRH), leading to decreased luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion. This results in testicular atrophy, infertility, and a host of systemic complications including hepatic dysfunction, cardiovascular disease, and psychiatric disturbances.
Alternatively, endogenous sources of elevated testosterone include Leydig cell tumors or adrenal tumors producing androgens. These conditions require imaging and biochemical evaluation to distinguish between testicular and adrenal etiologies. Elevated 17-hydroxyprogesterone or dehydroepiandrosterone sulfate (DHEA-S) levels can help identify adrenal involvement No workaround needed..
Counterintuitive, but true The details matter here..
Low Testosterone in Testicular Bodies (Hypogonadism)
Male hypogonadism is classified as either primary (testicular failure) or secondary (hypothalamic-pituitary dysfunction). Primary hypogonadism presents with elevated LH and FSH due to lack of negative feedback, whereas secondary hypogonadism features low or inappropriately normal gonadotropins. Common causes include Klinefelter syndrome, mumps orchitis, chemotherapy, and age-related decline.
Symptoms range from decreased muscle mass and bone density to mood changes, reduced libido, and infertility. Diagnosis relies on morning total and free testosterone measurements, followed by confirmatory tests if indicated. Treatment involves testosterone replacement therapy (TRT), made for maintain physiologic levels while minimizing adverse effects. Even so, TRT suppresses spermatogenesis, so fertility preservation strategies—such as gonadotropin therapy or sperm cryopreservation—should be considered before initiating treatment.
Worth pausing on this one.
Therapeutic Approaches: Restoring Equilibrium
Understanding the nuanced roles of testosterone across sexes informs targeted therapeutic interventions But it adds up..
For Ovarian Bodies:
- Anti-androgens: Spironolactone, finasteride, or cyproterone acetate block androgen action and are mainstays in managing hirsutism and acne associated with PCOS.
- Insulin-sensitizing agents: Metformin improves insulin sensitivity, indirectly reducing ovarian androgen production.
- Oral contraceptives: Combined estrogen-progestin formulations increase SHBG, effectively lowering free testosterone levels.
- Emerging therapies: GLP-1 receptor agonists and SGLT2 inhibitors show promise in addressing metabolic components of hyperandrogenism.
For Testicular Bodies:
- Testosterone replacement therapy (TRT): Available in various formulations (gels, patches, injections, pellets), TRT aims to restore energy, mood, libido, and body composition. Regular monitoring ensures safety and efficacy.
- Fertility considerations: Men desiring future fertility should avoid TRT or use adjunctive therapies like human chorionic gonadotropin (hCG) or selective estrogen receptor modulators (SERMs) to stimulate endogenous testosterone production.
- Lifestyle modifications: Weight loss, resistance training, adequate sleep, and stress management enhance natural testosterone levels and overall health outcomes.
Conclusion
Testosterone is far more than a sex-specific hormone governing reproduction and secondary sexual characteristics. Its influence extends deeply into metabolism, cognition, musculoskeletal integrity, and cardiovascular function—all modulated by involved feedback mechanisms and influenced by sex-specific physiology. Recognizing that both ovaries and testes contribute meaningfully to circulating androgen pools challenges outdated paradigms and underscores the importance of individualized assessment No workaround needed..
Clinicians must move beyond simplistic interpretations of "high" or "low" total testosterone values, instead focusing on symptom correlation,
symptom correlation, free hormone bioavailability, and the broader clinical context—including age, body composition, metabolic health, and patient goals. Equally critical is acknowledging the distinct physiological roles and reference ranges for ovarian versus testicular bodies, ensuring that diagnostic thresholds and therapeutic targets reflect biological reality rather than historical bias.
As research continues to illuminate testosterone’s pleiotropic effects—from neuroprotection and mitochondrial function to immune modulation and tissue repair—the clinical approach must evolve toward precision endocrinology. This means integrating advanced biomarkers, genetic profiling, and longitudinal monitoring to tailor interventions that optimize hormonal equilibrium across the lifespan.
When all is said and done, testosterone should be viewed not in isolation, but as a central node within a dynamic endocrine network. By embracing its complexity and respecting its sex-dimorphic nuances, clinicians can deliver more effective, equitable, and patient-centered care—restoring not just hormone levels, but holistic well-being That's the part that actually makes a difference..
