Hormone replacement therapy (female-to-male)
Hormone replacement therapy (HRT) for transgender and transsexual people replaces the hormones naturally occurring in their bodies with those of the other sex. However, not all cases of hormone replacement therapy are used by transgendered people. Some reasons for this include men who wish to have a hair-free body, as a result of less of the testosterone, androgens in their body. Its purpose is to cause the development of the secondary sex characteristics of the desired gender. It can not undo the changes produced by the first natural occurring puberty of transgender people, this is done by sexual reassignment surgery and for transwomen by epilation. Some intersex people also receive HRT, either starting in childhood to confirm the gender they were assigned, or later, if this assignment has proven to be incorrect.
While some argue that hormonal therapy does not truly masculinize or feminize, the question is one of definitions. If by masculinize and feminize one means to completely reproduce the male or female biological state, that cannot be done with current medical or surgical therapy. However, the goal of HRT, and indeed all somatic treatments, is to provide patients with a more satisfying body that is more congruent with their true psychological gender identity. It should be noted that the effects of hormonal therapy are often much more satisfying to transgender men than transgender women. It is easier to produce secondary male sexual characteristics with androgens than it is to rid transgender women of those established characteristics.

# Formal requirements for HRT
The requirements for hormone replacement therapy vary immensely, often at least a certain time of psychological counselling is required, and so is a time of living in the desired gender role, if that is at all possible, in order to assure that they can psychologically function in that gender role. This period is sometimes called the Real Life Experience (RLE). See also Standards of care for gender identity disorders.
Some individuals choose to self-administer their medication ("do-it-yourself"), often because available doctors have too little experience in this matter, or no doctor is available in the first place. Sometimes, trans persons choose to self-administer because their doctor will not prescribe hormones without a letter from the patient's therapist stating that the patient meets the diagnostic criteria for GID and is making an informed decision to transition. Many therapists require at least 3 months of continuous psychotherapy and/or a real life test in order to write such a letter as is suggested in the HBIGDA Standards of Care. In these circumstances, the individual may self-administer until they can get these authorizations, feeling that they shouldn't have to wait for a medical professional to be convinced of their situation. In addition, as many individuals must pay for evaluation and care out-of-pocket, expense can also be prohibitive to pursuing such therapy.
However, self-administration of hormones is potentially dangerous. Individuals seeking physicians who are knowledgeable and willing to treat transgender patients may wish to consult transgender support groups or a directory of LGBT-friendly doctors, in the USA for example the Gay and Lesbian Medical Association's referral service at GLMA.org.

# Changes established at puberty
A number of skeletal and cartilaginous changes take place after the onset of puberty at various rates and times. Sometime in the late teen years epiphyseal clusure (in other words, the ends of bones are fused closed) takes place and the length of bones is fixed for life.  Consequently total height and the length of arms, legs, hands, and feet are not affected by HRT.  However, details of bone shape change throughout life, bones becoming heavier and more deeply sculptured under the influence of testosterone.  Many of these differences are described in the Desmond Morris book Manwatching.
- Pelvis:  The pelvis in females tends to be wider than in males and tilted forward; the pelvis in males tends to be more circular and tilted upwards.
- Hands:  Male hands and feet tend to be larger than female hands and feet in persons of equal height.
- Upper Arm:  The upper arm in females tends to be significantly longer (about 1") than in males of the same height.
- Head:  Females tend to have smaller heads than males of the same height.
- Chest:  Female ribcages tend to be narrower than those of males in the same height.
Facial changes develop gradually over time, and sexual dimorphism (physical difference between the sexes) tends to increase with age.  Within a population of similar body size and ethnicity:
- Brow:  Males tend to develop heavier bony brows than females.
- Cheeks:  Female cheeks tend to be fuller and more rounded.  Under the influence of estrogen, fat is deposited beneath the skin and overall facial and body contours become softer.
- Nose:  The tips of the nasal bones tend to grow more in males than females, creating a larger (longer or wider) nose.
- Jaw:  The jaw in males tends to grow wider and more deeply sculptured than in females.
- Larynx: At puberty, the bones and cartilage of the voicebox tend to enlarge less in females than males.  In some males, the larynx becomes visible as a bony "adam's apple."
- Lips:  Females tend to have thicker, fleshier lips than males of the same size.

# Changes
For transmen, taking androgens (i.e. testosterone) causes reversible and irreversible changes.

## Irreversible changes
- deepening of the voice,
- growth of facial and body hair,
- male pattern baldness (in some individuals),
- an enlargement of the clitoris,
- growth spurt and closure of growth plates if given before the end of puberty, and
- possible shrinking and/or softening of breasts, although this is due to changes in fat tissue.

## Reversible changes
- increased libido,
- redistribution of body fat,
- cessation of ovulation and menstruation,
- further muscle development (especially upper body),
- increased sweat and changes in body odor,
- prominence of veins and coarser skin,
- acne (especially in the first few years of therapy),
- alterations in blood lipids (cholesterol and triglycerides), and
- increased red blood cell count.
The psychological changes are harder to define, since HRT is usually the first physical action that takes place when transitioning. This fact alone has a significant psychological impact, which is hard to distinguish from hormonally induced changes. Most transmen report an increase of energy and an increased sex drive. Many also report feeling more confident.
While a high level of testosterone is often associated with an increase in aggression, this is not a noticeable effect in most transmen.  HRT doses of testosterone are much lower than the typical doses taken by steroid-using athletes, and create testosterone levels comparable to those of most non-trans men.  These levels of testosterone have not been proven to cause more aggression than comparable levels of estrogen.  It is assumed that the effect of the start of physical treatment is such a relief, and decreases pre-existing aggression so much, that the overall level of aggression actually decreases.
Some transmen are unable to pass as men without hormones. The most commonly cited reason for this is that their voice may reveal them.

# Contraindications
Several contraindications to androgen therapy exist. An absolute medical contraindication is pregnancy
Relative medical contraindications are:
- androgen sensitive epilepsy,
- migraines,
- sleep apnea,
- polycythemia (elevated red blood cell count,)
- cardiac failure, renal failure, or severe hypertension susceptible to salt retention and fluid overload
- significant liver disease
- coronary artery disease or risk factors for CAD
- history of uterine cancer
- bleeding disorders (for injected testosterone)
- significant history of violent behavior
- history of breast cancer (testosterone has anti-proliferative effects on most but not all breast cancers)

# Types of androgen therapy
The half-life of testosterone in blood is about 70 minutes, so it is necessary to have a continuous supply of the hormone for masculinization.

## Injected
'Depot' drug formulations are created by mixing a substance with the drug that slows its release and prolongs the action of the drug. The two primarily used forms in the US are the testosterone esters testosterone cypionate (Depo-Testosterone) and testosterone enanthate (Delatestryl) which are almost interchangeable. Enanthate is purported to be slightly better with respect to even testosterone release, but this is probably more of a concern for bodybuilders who use the drugs at higher doses (250-1000 mg/week) than the replacement doses used by transgender men (50-100mg/week.) They are mixed with different oils, so some individuals may tolerate one better than the other. Enanthate costs more than cypionate and is more typically the one prescribed for hypogonadal males in the US. Cypionate is more popular in the US than elsewhere (especially amongst bodybuilders.) Other formulations exist but are more difficult to come by in the US. Sustanon is a formulation that mixes shorter acting and longer acting testosterone preparations that gives more even levels of testosterone with injections given every three weeks. A newly marketed formulation of injected testosterone available in Europe, Nebido (testosterone undecanoate in oil) provides significantly improved testosterone delivery with far less variation outside the eugonadal range than other formulations with injections required only four times yearly. However, each quarterly dose requires injection of 4ml which may require multiple simultaneous injections.  Nebido is also much more expensive and currently unavailable in the United States.
The adverse side effects of injected testosterone esters are generally associated with high peak levels in the first few days after an injection. Some side effects may be ameliorated by using a shorter dosing interval (weekly or every ten days instead of twice monthly with enanthate or cypionate.) 100 mg weekly gives a much lower peak level of testosterone than does 200 mg every two weeks, while still maintaining the same total dose of androgen. This benefit must be weighed against the discomfort and inconvenience of doubling the number of injections.
Injected testosterone esters should be started at a low dose and titrated upwards based on trough levels (blood levels drawn just before your next shot.) A trough level of 500 ng/dl is sought. (Normal range for a biological male is  290 to 900 ng/dl.)

## Transdermal
Both testosterone patches and gels are available. Both approximate normal physiological levels of testosterone better than the higher peaks associated with injection. Both can cause local skin irritation (more so with the patches.)
Patches slowly diffuse testosterone through the skin and are replaced daily. The cost varies, as with all medication, from country to country, it is about $150/month in the US, and about 60 Euros in Germany.
Transdermal testosterone is available in the United States under the brand names Androgel and Testim. Both are absorbed quickly when applied and produce a temporary drug depot in the skin which diffuses into the circulation, peaking at 4 hours and decreasing slowly over the rest of the day. The cost varies, as with all medication, from country to country, it is about $150/month in the US for either brand name drug. However, certain pharmacies are able to compound the drug more cheaply.
Transdermal testosterone poses a risk of inadvertent exposure to others who come in contact with the patient's skin. This is most important for patients whose intimate partners are pregnant or those who are parents of young children as both of these groups are more vulnerable to the masculinizing effects of androgens. Case reports of significant virilization of young children after exposure to topical androgen preparations (both prescription and 'supplement' products) used by their caregivers demonstrates this very real risk.

## Testosterone pellets
6-12 pellets are inserted under the skin every three months. This must be done in a physicians office, but is a relatively minor procedure done under local anesthetic. Pellets cost about $20 each, so the cost is greater than injected testosterone when the cost of the physician visit and procedure are included. The primary advantages of Testopel are that it gives a much more constant blood level of testosterone yet requires attention only four times yearly.

## Oral
Not frequently used in the US, sometimes used in Europe. Once absorbed from the GI tract testosterone is shunted (at very high blood levels) to the liver where it can cause liver damage and worsens some of the adverse effects of testosterone - lower SHBG levels, lower HDL (good) cholesterol. In addition, the first pass metabolism of the liver also may result in testosterone levels too low to provide satisfactory masculinization and suppress menses. The safest of the oral formulations is Andriol (testosterone undecanoate) which is not available in the US.

## Sublingual/Buccal
In 2003 the FDA approved a buccal form of testosterone (Striant.) Sublingual testosterone can also be made by some compounding pharmacies. Cost for Striant is greater than other formulations ($180-210/month.) Testosterone is absorbed through the oral mucosa and avoids the 'first pass metabolism' in the liver which is cause of many of the adverse effect with oral testosterone. The lozenges can cause gum irritation, taste changes, and headache but most side effects diminish after two weeks. The lozenge is 'mucoadhesive' and must be applied twice daily.

# Non-testosterone hormonal therapy

## GnRH agonists
In both sexes, the hypothalamus releases GnRH (gonadotropin-releasing hormone) to stimulate the pituitary to produce LH (luteinizing hormone) and FSH (follicle stimulating hormone) which in turn cause the gonads to produce sex steroids. In adolescents of either sex with relevant indicators, GnRH agonists, such as nafarelin can be used to suspend the advance of sex steroid induced, inappropriate pubertal changes for a period without inducing any changes in the gender-appropriate direction. GnRH agonists work by initially over stimulating the pituitary then rapidly desensitizing it to the effects of GnRH. Over a period of weeks, gonadal androgen production is greatly reduced. There is considerable controversy over the earliest age, and for how long it is clinically, morally and legally safe to do this. The Harry Benjamin International Gender Dysphoria Association Standards of Care permit from Tanner Stage 2, but do not allow the addition of gender-appropriate hormones until 16, which could be five or more years. The sex steroids do have important other functions. The high cost of GnRH agonists is often a significant factor.

## Progestin injections
Depo-Provera (depot medroxyprogesterone acetate, or DMPA) may be injected every three months just as it is used for contraception. Generally after the first cycle, menses are greatly reduced or eliminated. This may be useful for transgender men prior to initiation of testosterone therapy.

## Supplements
Andro Pro-hormones: Androstenedione, 4-androstenediol, 5-androstenediol, 19-androstenediol, and 19-norandrostenediol are sold as supplements that are purported to increase serum testosterone, increase muscle mass, decrease fat, elevate mood, and increase sexual performance (i.e. many of the effects transgender men seek with androgen therapy.) However, there is no good medical evidence that the pro-hormones do any of these things. However, there is evidence that ingestion of these substances can cause elevated estrogen levels, and decreases in HDL (good) cholesterol.

# Testosterone effects

## Cardiovascular
- In biological men, testosterone levels that are either significantly above or below normal are associated with increase cardiovascular risk. This may be causative or simply a correlation.
- A single retrospective study in the medical literature of 293 transmen treated with testosterone (range of 2 months to 41 years) by the Amsterdam Gender Dysphoria Clinic from 1975 to 1994 showed no increase in cardiovascular mortality or morbidity when compared with the general female Dutch population. (As with all scientific studies, this does not conclusively prove that no causal link exists. A small to moderate detrimental effect remains a possibility, though a very large effect is more unlikely.)
- Androgen therapy does adversely affect the blood lipid profile by causing decreases in HDL (good) cholesterol, increases in LDL (bad) cholesterol, and increases in triglycerides.
- Androgen therapy redistributes the fat toward abdominal obesity, which is associated with increased cardiovascular risk rather than fat carried on the buttocks and hips.
- Androgen therapy can cause weight gain and decreased insulin sensitivity (perhaps worsening a predisposition to develop Type II diabetes.)
- Androgen therapy effects are not all negative, however. Acutely it causes dilation of the coronary arteries, and in men with testosterone levels within the normal physiological range, higher levels are actually associated with a slight decrease in cardiovascular disease.
- Supra-physiological levels of androgens (generally due to abuse) are associated with significantly increased risks of strokes and heart attacks (even in the young.) More is not better!
- Cardiovascular risk factors are more than additive. (If high blood pressure is worth 10 and smoking is worth 10, together they are worth more than 20.) So for transgendered men, the addition of risk with androgen therapy makes improving modifiable risk factors more important.
- The most important modifiable risk factor for many men is smoking.

## Hair
- The action of testosterone on hair follicles is mainly due to the more potent androgen, dihydrotestosterone, DHT.
- With androgen therapy, genetics primarily determines how much hair will develop (and where) as well as whether male pattern baldness will develop.
- Testosterone is converted (within the cells of the hair follicle's dermal papilla) by 5-alpha reductase to DHT. There are two forms of this enzyme: type 1 and 2. However, type 2 is the form that is important to the development of male pattern baldness. Male pseudohermaphrodites with congenital deficiency of type 2 5-alpha reductase (but functional Type 1) never develop male pattern baldness.
- Propecia (Finasteride) and Avodart (Dutasteride) are Type-2, 5-a-Reductase inhibitors that work by blocking the conversion of testosterone to DHT. While they will not make facial hair growth that has occurred regress, they may slow or prevent further development of new facial hair. Finasteride is sold as 5mg tablets as Proscar which is used to treat prostate enlargement and Propecia as 1 mg tablet to treat baldness. The cost of 'Propecia' per mg is significantly higher than 'Proscar' so some patients split tablets into quarters. At the 1-1.25mg/day dose it may also decrease libido.
- Saw palmetto is a naturally occurring 5-alpha reductase inhibitor which is used by some to treat male pattern baldness and prostate enlargement.
- Rogaine (Minoxidil  available without a prescription in the US) is a topical preparation of a potent blood pressure medicine. It is sold as 2% and 5% solutions. The 5% solution is not recommended for use by women because it may cause the adverse effect of unwanted facial hair growth in a small percentage of women. It may also cause skin irritation and itching. One ml is applied twice daily to the scalp (predominantly in the areas where hair loss is greatest.) It may take several months to show effects and may cause a slight paradoxical worsening of hair loss initially (that does eventually recover.)
With either minoxidil or finasteride the beneficial effect will be lost within months upon ceasing use of product. With either, best results occur when they are started before significant hair loss has occurred.

## Gynecological effects
- Menses should cease within 5 months of testosterone therapy (often sooner.) If bleeding continues past 5 months, transmen must see a gynecologist.
- Clitoromegaly occurs, and frequently reaches its apex within 2-3 years of therapy. Sizes generally range from 3-8 cm with 4-5 cm being about average. This is genetically determined, but some physicians advocate topical clitoral testosterone as an adjunct to growth before metaidioplasty. However, this testosterone is absorbed and should be calculated into your total regimen.
- After long-term androgen therapy, ovaries may develop polycystic ovary syndrome (PCOS) morphology. (In both PCOS and transgender men there is an up-regulation of testosterone receptors in the ovaries.)
- Untreated PCOS is associated with a possibly increased risk of endometrial cancer as well as decreased fertility.
- It is unknown whether the risk of ovarian cancer is increased, decreased or unchanged in transgender men compared to women. It is unlikely to be determined in the near future because ovarian cancer is a relatively rare disease and the population of transgender men is too small to do the appropriate study. However, it has been recommended by some physicians that transgender men have an oophorectomy within 2-5 years of starting androgen therapy due to the possible increased risk. (Note: Testosterone dose can frequently be decreased after oophorectomy.)
- The risk of endometrial cancer is similarly unknown. However, A high prevalence of endometrial hyperplasia has been noted in a small study of transgender men undergoing hysterectomy. (Futterweit W, and Deligdisch L. Histopathological effects of exogenously administered testosterone in 19 female to male transsexuals. J Clin Endo & Metab. 62(1):16-21. 1986.)
Frequently the first sign of endometrial cancer is bleeding in post-menopausal women. Transgender men who have any bleeding after the cessation of menses with androgen therapy should have an endometrial biopsy (and possibly an ultrasound) done to rule-out endometrial cancer.
- Some sources recommend endometrial ultrasounds every two years. Testosterone usually causes atrophy of the endometrium. Any transgender man with an endometrium that is not thinned on ultrasound should have a biopsy to evaluate for endometrial cancer and possibly use progesterone to cause sloughing of the endometrium. Vaginal bleeding from progesterone may be emotionally uncomfortable for a transman, but it is preferable to developing endometrial cancer.
- Until recently, any adult with a uterus/cervix was advised to have a Pap smear yearly. This interval might be increased to every 2-3 years for certain people on the advice of a gynecologist.  However, recent research has linked cervical cancer to a sexually transmitted virus; transmen who have never had vaginal sex may not be at risk.  However, since the long-term effects of testosterone on cervical tissues are not well understood, Pap smears may be considered a general precaution.
- Some transgender men report a decrease in breast size with androgen therapy. However, no morphological changes were found when this was studied and likely it is due to loss of fat in the breasts.
- Androgen therapy (and suppression of estrogen production) may cause vaginal atrophy and dryness, which may result in dyspareunia (painful vaginal intercourse.) This can be alleviated with topical estrogen cream.
- Most transgender men report a significantly increased libido. Some report that this decreases somewhat after several years on testosterone. (Natural testosterone levels peak in women just before ovulation which may account for the mid-cycle increase in libido many women experience.)

## Childbearing
- As the age at which transgender people begin therapy decreases, retention of reproductive potential becomes more important.
- If a transgender man has not undergone hysterectomy and oophorectomy, he may regain fertility on cessation of testosterone. With the ovarian changes of long-term androgen therapy, however it may require months of cessation of testosterone and possibly assistive reproductive technology to become pregnant. Testosterone must be withheld for the duration of pregnancy.
- If a transgender man is planning on having a hysterectomy/oophorectomy, future reproduction may still be preserved by:
Oocyte banking  hormonal stimulation to hyper-ovulate with transvaginal oocyte harvest for freezing. Very poor survival of banked oocytes.
Embryo banking  oocyte harvest as above with immediate fertilization and banking of the embryo. Much better survival, but the sperm donor must be chosen before oophorectomy.
Ovarian tissue banking  probably the best option. Ovarian tissue is frozen after oophorectomy. Even after long term androgen therapy, ovaries usually retain usable follicles. Eventual use of frozen ovaries will require replantation into the transgender man for stimulation and harvest, but may eventually be possible in a lab as techniques for tissue culture improve.
- Oocyte banking  hormonal stimulation to hyper-ovulate with transvaginal oocyte harvest for freezing. Very poor survival of banked oocytes.
- Embryo banking  oocyte harvest as above with immediate fertilization and banking of the embryo. Much better survival, but the sperm donor must be chosen before oophorectomy.
- Ovarian tissue banking  probably the best option. Ovarian tissue is frozen after oophorectomy. Even after long term androgen therapy, ovaries usually retain usable follicles. Eventual use of frozen ovaries will require replantation into the transgender man for stimulation and harvest, but may eventually be possible in a lab as techniques for tissue culture improve.

## Bone
- Both estrogens and androgens are necessary in both biological males and females for healthy bone. (Young healthy women produce about 10 mg of testosterone monthly. Higher bone mineral density in males is associated with higher serum estrogen.)
- Bone is not static. It is constantly being reabsorbed and created. Osteoporosis results when bone formation occurs at a rate less than bone reabsorption.
- Estrogen is the predominant sex hormone that slows bone loss (even in men.)
- Both estrogen and testosterone help stimulate bone formation (T, especially at puberty.)
- Testosterone may cause an increase in cortical bone thickness in transgender men (however this does not necessarily translate to a greater mechanical stability.)
- Transgender men who have been oophorectomized must continue androgen therapy to avoid premature osteoporosis. Estrogen supplementation is theoretically not usually necessary, as some of the injected testosterone will be aromatized into estrogen sufficient to maintain bone (as it does in biological men.) However, a single small study of transmen after oophorectomy demonstrated that androgens alone may be insufficient to retard bone loss. (van Kesteren P, et al. Long-term follow-up of bone mineral density and bone metabolism in transsexuals treated with cross-sex hormones. Clin Endocrin. 48(3):347-54. 1998.) It is likely the case that pre-oophorectomy, residual estrogen production is protective. However, after oophorectomy, some transmen may have insufficient estrogen to retard bone loss.
- Some physicians advocate a Dexa (bone density) scan at the time of oophorectomy and every year or two thereafter to diagnose osteoporosis before it becomes severe enough to be symptomatic. This is important because treatment of osteoporosis is most effective if done early.
- Daily calcium supplementation and possibly Vitamin D is probably a good idea for most transgender men, but it is even more important after removal of the ovaries.

## Drug interactions
Testosterone (and all the sex steroids) are metabolized by the Cytochrome P-450 enzyme system in the liver. (Specifically CYP3A.)
There are certain drugs that increase or decrease the activity of this enzyme and may cause increased or decreased levels of testosterone and other sex steroids.
- Cyt P-450 Inducers  May cause decreased levels of testosterone (and other sex steroid) levels: Phenobarbital and Dilantin (seizure medicines,) Rifampin (antibiotic,) and Alcohol!
- Cyt P-450 Inhibitors  May cause increased levels of testosterone: Serzone, Prozac, Paxil (antidepressants,) Sporanox, Diflucan, and other azole antifungals, Tagamet (anti-ulcer agent that can cause gynecomastia in men because of this effect.) Biaxin and other erythromycin type antibiotics, Protease Inhibitors (HIV treatment.)
Testosterone can also alter the effects of other drugs:
- Increases the blood thinning effect of Coumadin (warfarin.)
- Decreases the effectiveness of Inderal (propranolol) a blood-pressure medicine.
- Increases the effect of some oral medicines for diabetes and can cause dangerously low blood sugar levels.
Because of these interactions, it is imperative that transmen tell any health care provider that he sees for any reason that he is on androgen therapy (and any other medication or supplement that he takes.)

## Obstructive sleep apnea
- OSA may be worsened or unmasked by androgen therapy.
- Risk is greater in transgender men who are obese, smoke, or have COPD (Chronic Obstructive Pulmonary Disease.)
- Untreated OSA may have significant adverse effects on the heart, blood pressure, mood, and may cause headaches and worsen seizure disorders.
- Symptoms of OSA are noisy sleeping (snoring,) excessive daytime sleepiness, morning headache, personality changes, and problems with judgment, memory, and attention.

## Polycythemia
- Increased red blood cell mass usually from overproduction by the bone marrow.
- Testosterone (frequently in large doses) was previously used to treat anemia from bone marrow failure.
- A transgender mans hematocrit (the percentage of whole blood made up of red blood cells) should be judged against normal age adjusted values for men.
- Therapy is via phlebotomy (periodic therapeutic blood draws similar to blood donation.)
- Tendency to become polycythemic worsens with age.
- Worse with injected testosterone (especially with longer intervals between doses) than with oral, transdermal, or Testopel. (Increase in RBCs occurs with the very high peaks from injection. So decreasing dose and interval to 7-10 days instead of 14 may help.)
- Severe polycythemia predisposes to both venous and arterial thrombosis (blood clots) such as: deep venous thrombosis, pulmonary embolism, heart attack, and stroke.
- Aspirin may decrease the risk

## Skin
- Increased activity of oil and sweat glands.
- Change in body odor  less sweet and musky, more metallic and acrid.
- If severe odor is a problem, an antibacterial soap like chlorhexidine may be used in the armpits when showering. After 1-2 weeks of daily use, a noticeable decrease in odor should occur.
- Acne: generally worse the first few years of testosterone therapy (mimicking a second puberty.) Can be treated with standard acne therapy. Initial treatment is with increased cleansing (at least twice daily) with an anti-acne or oil reducing scrub. If this doesnt work, additional therapy may be prescribed by a physician.
- Some physicians see acne as a contraindication to increasing testosterone dose.

## Gastrointestinal
- There is a risk of liver damage and liver cancer with all testosterone formulations, but this is minimal with all forms except oral or unless very high levels are administered. However, as with any drug that carries even a small risk of liver damage, liver function tests (or at least ALT) should be periodically monitored.

## Neurological/Psychiatric
- Headaches: Pre-existing migraine headaches can be significantly worsened with androgen therapy. Headaches can also become problematic in men without prior headache disorders.
- Epilepsy: some seizure disorders are androgen-dependent. These may be worsened or (very rarely) unmasked with androgen therapy.
- Sleep deprivation worsens almost all seizure disorders, so concurrent obstructive sleep apnea caused or worsened by androgen therapy may also be responsible.
- Some transgender men report mood swings, increased anger, and increased aggressiveness after starting androgen therapy (similarly to the effects reported with body builders who abuse androgens.) This is much less severe however than the roid rage experienced by bodybuilders because with transgender men significantly supraphysiologic levels are not present.
- Many transgender men, however, report improved mood, decreased emotional lability, and a lessening of anger and aggression. Likely this is not a physiologic effect but rather the alleviation of emotional distress from long-standing gender dysphoria.
- Recent studies have indicated that cross-hormone therapy in transmen may result in an increase in brain volume towards male proportions.

## Metabolic
- Testosterone increases body weight (and increases appetite.) The form that this weight gain will take depends on diet and exercise as well as genetic factors. Since testosterone has anabolic effects, gain of lean muscle mass will be easier than it previously was for transgender men. Moderate amounts of exercise will cause greater gains and will ameliorate some of the adverse effects of testosterone.
- Many transgender men report an increased energy level, decreased need for sleep, and increased alertness after testosterone therapy.
- In biological men, abnormally high or low levels of testosterone are both associated with insulin resistance (which eventually can result in Type II diabetes.) So mid-normal levels of testosterone are the target for androgen therapy.
- In women, increased levels of either estrogen or androgens are associated with decreased insulin sensitivity (which may predispose to diabetes.) In a study of transgender males and females, decreased insulin sensitivity was found in both populations after four months or hormonal treatment. (Polderman K, et al. Induction of insulin resistance by androgens and estrogens. J Clin Endo Metab. 79(1):265-71. 1994.)