hormone injections
Testosterone injections are a common way to administer masculinizing hormone therapy.
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  • Masculinizing hormone therapy can help induce masculine characteristics — like a deeper voice, more facial hair, and genital changes — to better match your gender identity. 
  • Testosterone — in the form of injections, gels, or patches — is the only hormone administered during masculinizing hormone therapy. 
  • There are some health risks associated with taking testosterone, such as blood clots, so it’s important to check in with a qualified doctor before, during, and after the procedure. 
  • This article was medically reviewed by Ravi Iyengar, MD, an endocrinologist at Rush University Medical Center with clinical expertise in transgender medicine.
  • Visit Insider’s Health Reference library for more advice.

Masculinizing hormone therapy is one way those who were assigned female at birth can achieve masculine body characteristics to help them feel more at ease in their skin. Here’s what you need to know about this common aspect of transmasculine gender-affirming therapy. 

What is masculinizing hormone therapy? 

Testosterone is the only hormone people use in masculinizing hormone therapy, says Amy Weimer, MD, a primary care physician with a clinical interest in transgender care at UCLA Health. 

There are three main ways to take testosterone: 

  • Injections. Injections are usually required once a week. Subcutaneous (under the skin) injections are an effective and often preferred form of administering testosterone, when compared to intramuscular injections, which are more painful, according to a 2015 study published in The Journal of Clinical Endocrinology and Metabolism. 
  • Gels. Testosterone gel, such as AndroGel, looks and smells like hand sanitizer, but it is rubbed into the arms, belly, or legs. The testosterone seeps through the skin and enters the bloodstream. However, only 10% of the testosterone from the gel actually enters the body, making it an inefficient way to administer testosterone. 
  • Patches. Testosterone patches are placed directly onto the skin to deliver testosterone to the body, and they must be left in place for 24 hours. They forgo users requiring needles and prevent accidentally touching others with testosterone.

 

In all, transmasculine gender-affirming therapy involves increasing someone’s testosterone level from a typical female range to a male range, which is about 300 to 1,000 ng/dl. 

10 changes to expect from masculinizing hormone therapy 

Depending on the dose, frequency, chosen method, and the person’s genetics, you may start to see masculinizing changes within the first week or a few months. Here’s a timeline showing some of the changes you can expect: 

how the body changes from masculinizing hormone therapy graphic
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1. Skin differences. Your skin will thicken and become more oily. You may also notice more acne due to increased oil production. 

2. Hair growth. Existing facial and body hair will thicken, darken, and grow at a faster rate. More hair will grow on the chest, back, arms, legs, and rest of the body. You'll start to grow a more pronounced mustache and beard too. Some may also experience male pattern baldness if it runs in the family. 

3. Deepening of voice. Your vocal cords will thicken and lengthen, leading to a deeper, more masculine voice. The voice may sound hoarse or crack within the first three to six months before breaking, akin to a young male's voice during puberty. 

4. Changing facial features. Cheekbones tend to lower and the jaw becomes more prominent. Changing facial features become noticeable after three months of hormone therapy, according to a 2019 study published in the Journal of Sexual Medicine. 

5. Body fat redistribution. Taking testosterone decreases the body's fat mass, according to a 2018 study published in the European Society of Endocrinology. This is most noticeable in the hips, legs, arms, and face. 

6. Muscular changes. Those who take testosterone will notice it's easier to build muscle when exercising, Weimer says. Muscles may also become more pronounced as body fat is redistributed. 

7. Cessation of menses. Taking testosterone will make periods become lighter, shorter, and arrive later before stopping them completely.

8. Reduced possibility of getting pregnant. Testosterone reduces the likelihood of becoming pregnant, but it doesn't eliminate the possibility completely. Transmasculine individuals with ovaries and a uterus can still get pregnant, even if testosterone stops menstruation.

Use condoms (either external or internal) and dental dams every time you have sex to reduce the risk of STDs and pregnancy. Those who go off testosterone therapy may become pregnant again with the return of menses, but you should talk to your doctor before attempting to get pregnant. 

9. Increased libido. Taking testosterone increases sex drive, says Weimer. A 2016 study published in Culture, Health & Sexuality finds that in a sample of 122 transgender men, nearly 69% associated testosterone with new sexual behaviors and 72% experienced an increase in sexual activity. 

Since testosterone thins the walls of the vaginal canal, penetrative sex can cause the tissue to tear. Torn vaginal tissue increases the risk of getting STDs or HIV. Using estrogen cream can thicken the walls of the vagina and reduce the risk of tearing. 

10. Genital changes. The cells that make up the clitoris will try to grow into a penis. Unlike a penis, the urethra will remain separate. However, the clitoris may grow one to two inches, though it can grow larger depending on your genetics. 

"They will take that shape, there will be that growth," says Joshua Safer, MD, an endocrinologist at the Center for Transgender Medicine and Surgery at Mount Sinai Hospital. "But it won't be the same as for someone who had testosterone from when they were in their mother's womb." 

The vaginal walls will also become thinner and more prone to tearing after starting testosterone. Natural lubrication also decreases. Some trans men also report pelvic pain, as testosterone could affect the uterus and pelvic muscles. 

Possible side effects and health risks 

"The main concern with testosterone levels is that they stimulate red blood cells and red blood cell growth," Safer says. 

Because testosterone increases the number of red blood cells, a hematocrit test must be done to ensure that red blood cell count remains under 50% of the total blood volume while undergoing testosterone hormone therapy. 

 

Excess red blood cells could obstruct how well the body absorbs oxygen in the blood, says Safer. It could also lead to an increased risk of blood clots. 

Some signs you're at risk for a blood clot includes: 

  • Swelling along a vein, especially in the leg
  • Pain in the leg, which may only be felt when standing or walking
  • An area in the leg that feels hot or swollen
  • Red or discolored skin 

Testosterone hormone therapy can also increase the risk of diabetes, cause or worsen headaches, and increase the risk of stroke, according to the Trans Care Project. However, the project states the extent of these risks is still unknown.

Takeaways

Overall, masculinizing hormone therapy with testosterone can help patients feel more at home in their own bodies. 

However, these physical changes will take time, and the exact process may be different depending on the individual and their metabolic and genetic makeup. 

Those seeking to start masculinizing hormone therapy can find a doctor aligned with the World Professional Association for Transgender Health (WPATH). WPATH is an organization devoted to promoting evidence-based care, education, and respect in transgender health, and there are over 100 WPATH experts in endocrinology in the US alone. 

Another resource to check out is Hudson's FTM Resource Guide, which not only includes more information on testosterone hormone therapy, but also tips on grooming and presenting as male, too. 

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