Testosterone Replacement Therapy (TRT): A Clinical Guide for Providers

Written by Empire Medical Training Editorial Team

Medically reviewed by Betsy Greenleaf, DO Board-Certified OB/GYN & Urogynecologist; Empire Director of Anti-Aging

Updated June 2026 ·12 min read

Testosterone replacement therapy (TRT) restores testosterone toward a normal physiologic range in patients with symptomatic deficiency. Although it is most associated with aging men, the underlying principle is broader: testosterone is one of the three primary sex hormones present in every patient, alongside estrogen and progesterone, and it influences bone density, lipid metabolism, mood, cognitive function, and cardiovascular health in both sexes. Done well, TRT relieves real symptoms. Done carelessly, it drives red blood cell counts up, stimulates hormone-sensitive tumors, and suppresses a patient's own production. The difference is clinical discipline.

This guide situates testosterone within the broader field of bioidentical hormone replacement therapy and is written for clinicians who want an accurate, practical overview. It is clinical education, not medical advice, and nothing here should be read as a treatment recommendation, protocol, or substitute for current standards of care and product labeling.

What is testosterone replacement therapy?

Testosterone is produced in the testes and adrenal glands in men, and in the ovaries and adrenals in women. Its receptors are widely distributed — in muscle, bone, skin, hair follicles, liver, brain, and reproductive tissue — which is why a single deficiency produces such a scattered constellation of symptoms, and why restoring it has effects far beyond libido. TRT supplies exogenous testosterone to bring a deficient patient back into the physiologic range.

The central clinical philosophy, as taught in Empire's hormone curriculum, is restraint. Testosterone makes patients feel good — it creates a genuine sense of wellness and energy — which is exactly why it is a controlled substance and why there is a temptation to keep raising the dose. The goal of TRT is to adjust a patient back to physiologic levels to reduce the risk of conversion to estrogen, hormone-sensitive cancers, testicular shrinkage, and receptor insensitivity — not to blunt the body's own production or push numbers ever higher. More is not better.

Low testosterone: causes, symptoms, and diagnosis

Testosterone declines naturally with age. Roughly 38% of men over 45 experience hypogonadism, compared with only about 7% of men under 40. In women, testosterone likewise falls with age as the ovaries begin to fail; after menopause, the majority of a woman's remaining testosterone is produced by the adrenal glands.

Causes

Low testosterone is not always a simple production problem. It can reflect issues anywhere along the hypothalamic-pituitary-gonadal axis, the effect of medications that interfere with testosterone production or metabolism, or excess conversion to estrogen. That last mechanism is worth emphasizing for providers: excess fat tissue contains aromatase, the enzyme that converts testosterone into estradiol, so an overweight man can present with simultaneously low testosterone and high estradiol — the testosterone he does make is being siphoned off into estrogen. Endocrine disruptors should also be considered in any patient whose labs do not make sense or who fails to respond as expected to therapy, especially men.

Symptoms

In men, low testosterone can present as reduced sex drive, difficulty with erections, low sperm count, fatigue and poor energy, decreased muscle mass, increased body fat, decreased bone density, and mood changes. In women, it can present as fatigue, decreased sex drive, mood changes, decreased muscle mass, increased body fat, menstrual irregularities, and reduced fertility.

Laboratory diagnosis

Diagnosis combines symptoms with lab work; neither alone is sufficient. The core measures are total testosterone and free testosterone, interpreted alongside related markers such as DHEA, estradiol (to assess aromatization), and sex hormone–binding globulin. While saliva testing is often described as the gold standard for hormone assessment generally, testosterone is the notable exception — serum is still the standard, and specialty serum testing may not be covered by insurance. A practical lesson from the clinic: labs and symptoms do not always agree. A patient can feel excellent with numbers that look low, or feel poorly with numbers that look normal, which is precisely why TRT is managed against both the clinical picture and the labs rather than chasing a single value. (We avoid publishing specific cutoff numbers here; reference ranges and interpretation are taught in Empire's training.)

How testosterone works in the body

Following the steroidogenesis pathway clarifies a great deal of TRT management. In a relaxed, parasympathetic state, cholesterol — the parent hormone — flows down the pathway into pregnenolone and progesterone, then into testosterone and the estrogens. This is not a one-way street: these hormones can interconvert. Testosterone is further metabolized into less active metabolites and into DHT (dihydrotestosterone), and in some individuals elevated DHT contributes to hair loss.

Two conversions dominate clinical decision-making. First, aromatization to estrogen: any testosterone given will partly convert into estradiol, which is why estrogen excess is a predictable consequence of testosterone therapy that must be monitored, not an afterthought. Second, conversion to DHT, the driver of androgenic side effects such as hair loss. Understanding where a given patient is shunting their testosterone — toward estrogen, toward DHT, or down a favorable pathway — is what separates competent replacement from blind dosing.

Delivery methods: pellets, injections, and gels

Testosterone can be replaced through several routes, each with distinct kinetics and trade-offs.

• Subcutaneous pellets — small, tablet-like compounds placed under the skin that release hormone slowly over roughly three months. Pellets are convenient and avoid the peaks and troughs of other methods by creating a steady state, and dosing can be customized. Their downsides: they can be more expensive, are not always covered by insurance, are difficult to reverse once placed, and absorption can vary from person to person, pharmacy to pharmacy, and batch to batch. See our dedicated guide to hormone pellet therapy for the full picture.
• Injectable esters — testosterone cypionate and enanthate are given on a periodic schedule (commonly around every two weeks), longer-acting depot forms exist, and short-acting propionate is dosed every few days. Injections offer flexible titration and are useful for bridging.
• Topical gels — applied daily, easy to adjust up or down, and a good option when fine control or a trial period is desired.
• Oral testosterone — generally not recommended, because oral testosterone has an affinity for the liver and is associated with liver toxicity.

A practical point that ties the routes together is the steady-state problem of pellets. Because pellets hold levels constant, patients can develop hormonal (receptor) insensitivity — they report the pellets "worked for a while and then stopped." Rather than simply escalating the pellet dose (which risks chasing the receptor out of the physiologic range), the curriculum teaches spacing pellet placement out and bridging with a daily, short-acting form such as a transdermal gel or injection to keep receptors sensitive. This interplay between delivery routes is one of the more nuanced parts of TRT management.

Benefits and the evidence behind them

When testosterone is genuinely deficient and properly restored, patients can see improvement across the symptom domains that brought them in: libido and sexual function, energy, mood, body composition (more lean muscle, less fat), and bone density — relevant for patients with or at risk of osteoporosis. Because testosterone receptors live in muscle, bone, brain, and reproductive tissue, the benefits track that distribution.

These benefits should be framed honestly. Improvement is most reliable in patients who are truly deficient, and several caveats apply. Libido, as noted, is multifactorial and may not respond to testosterone alone. Body-composition gains depend on the patient doing the work — the hormone is a lever, not a substitute for training and nutrition; a patient can normalize his testosterone and still "not see results in the gym" without resistance exercise. And benefit is not a license to push levels higher: once a patient is within the physiologic range, additional testosterone tends to add risk, not reward. The honest message to patients is that TRT can restore what deficiency took away, but it is not a performance-enhancing shortcut.

Risks and safety considerations

TRT has a real and manageable risk profile, and screening before the first prescription is non-negotiable. The major considerations:

• Erythrocytosis / polycythemia. Testosterone increases red blood cell count, and an elevated hematocrit raises the risk of a more viscous, thrombosis-prone bloodstream. TRT is contraindicated in patients with a high red blood count, and red cell indices must be monitored on therapy.
• Prostate considerations. Testosterone can stimulate hormone-sensitive prostate cancer, so TRT is contraindicated in active prostate cancer. Importantly, the broader role of testosterone in prostate cancer is not fully understood; patients should be current on prostate screening (including PSA and digital rectal exam where appropriate) before starting.
• Cardiovascular debate. Whether and how TRT affects cardiovascular risk has been genuinely debated in the literature. Testosterone can cause fluid retention, raise cholesterol, and is best avoided in severe heart disease; at the same time, observed rates of myocardial infarction, stroke, and DVT in appropriately monitored men have been low. The responsible stance is careful selection and surveillance rather than either alarmism or dismissal.
• Sleep apnea. Testosterone can worsen or precipitate sleep apnea and is contraindicated in untreated obstructive sleep apnea.
• Fertility suppression and testicular atrophy. Via the hypothalamic-pituitary-gonadal feedback loop, exogenous testosterone suppresses the body's own production and can cause testicular shrinkage. TRT is therefore not appropriate for men of childbearing intent who wish to preserve fertility; where raising levels without suppressing the axis is the goal, beta-hCG is an alternative approach. Excess testosterone can also produce acne, oily skin, hair loss, mood changes, and aggression.

Deliberately, this overview avoids specific dosing, titration schedules, and pellet milligram or insertion details — those belong in hands-on training and individualized clinical judgment, not a general educational page. The responsible summary is that TRT is effective and well-characterized but demands proper patient selection, screening, and ongoing monitoring.

Testosterone in women: the low-dose role

It surprises many providers that testosterone has a legitimate, if lower-profile, role in women. Every woman makes testosterone, and as the ovaries fail with age her levels decline, leaving the adrenals as the primary source after menopause. Symptomatic women — with fatigue, low libido, mood changes, decreased muscle mass, or increased body fat — may benefit from low-dose testosterone, frequently delivered as a low-dose topical or a smaller pellet, often considered alongside pellet therapy for other hormones.

Two points are essential. First, dosing in women is dramatically lower than in men, and excess produces predictable androgenic effects: irregular cycles, hirsutism, acne or oily skin, clitoral enlargement, and irritability. Second, and frequently overlooked, is uterine protection. Because testosterone (and DHEA) can convert into estrogen, a woman with a uterus receiving testosterone or DHEA needs uterine protection — for example, a progesterone-containing IUD — just as she would with estrogen supplementation. As with men, the same humility about libido applies: testosterone and DHEA are not, by themselves, the answer to low sex drive in women.

Candidacy and monitoring

Good candidates for TRT are symptomatic patients with confirmed deficiency: andropausal men with symptoms, patients with osteoporosis or conditions causing hormonal imbalance such as hypogonadism or premature menopause, and select women as above. Patients should be up to date on age-appropriate screenings — prostate, mammograms, Pap smears, colonoscopy — before therapy begins, and history should be reviewed for red flags such as atrial fibrillation that may shift the risk calculus.

Contraindications mirror the risks: hormone-sensitive cancers (notably prostate and breast), a history of blood clots, stroke, or significant heart disease, severe liver or kidney disease, untreated sleep apnea, high red blood count, and pregnancy or breastfeeding. Monitoring is structured around lab follow-up — for pellets, reassessment is generally considered within three to six months of placement — tracking total and free testosterone, estradiol (to catch aromatization), and red cell indices, and adjusting to keep levels within physiologic limits rather than reacting to symptoms alone. A recurring teaching point: do not chase symptoms with ever-higher doses; keep levels in range, manage conversion with measures such as aromatase support where indicated, and preserve receptor sensitivity by spacing therapy. The detailed protocols, conversion math, and pellet specifics are covered in Empire's hands-on training.

Training: doing TRT competently

Because testosterone is so easy to prescribe and so easy to mismanage, the clinical challenge is less about whether the science is sound and more about using it competently: confirming deficiency, selecting the right delivery route, managing aromatization and DHT conversion, screening prostate and red cell indices, and resisting the pull to chase symptoms with escalating doses. These are skills built through structured education and supervised practice, not learned from a label. Empire's curriculum — situated within the broader science of bioidentical hormone replacement therapy — is built around exactly this kind of practical judgment, and connects directly to hands-on hormone pellet training for providers who want to offer TRT responsibly.