Women can take testosterone as a cream, through a patch or in the form of pellet implants, which have the highest consistency of delivery. Synthesized from yams or soybeans, and compounded of pure, bioidentical testosterone, the pellets, each slightly larger than a grain of rice, are inserted just beneath the skin in the hip in a one-minute outpatient procedure. They dissolve slowly over three to four months, releasing small amounts of testosterone into the blood stream, but speeding up when needed by the body — during strenuous activities, for example — and slowing down during quiet times, a feature no other form of hormone therapy can provide.
Testosterone Injections, like many anabolic steroids, was classified as a controlled substance in 1991. Testosterone is administered parenterally in normal and delayed-release (depot) forms. In September 1995, the FDA approved testosterone transdermal patches (Androderm), and many transdermal forms and brands are now available including implants, gels, and topical solutions. A testosterone buccal system, Striant, was FDA-approved in July 2003; Striant is a mucoadhesive product that adheres to the buccal mucosa and provides a controlled and sustained release of testosterone. In May 2014, the FDA approved an intranasal gel formulation of testosterone (Natesto). A transdermal patch (Intrinsa) for hormone replacement in women is under investigation; the daily dosages used in women are much lower than for products used in males. The FDA refused approval for Intrinsa in 2004 stating that more data regarding safety, especially in relation to cardiovascular and breast health, where required.
We have studied the effect of a pharmacological dose of testosterone enanthate (3 --1 for 12 wk) on muscle mass and total-body potassium and on whole-body and muscle protein synthesis in normal male subjects. Muscle mass estimated by creatinine excretion increased in all nine subjects (20% mean increase, P less than ); total body potassium mass estimated by 40K counting increased in all subjects (12% mean increase, P less than ). In four subjects, a primed continuous infusion protocol with L-[1-13C]leucine was used to determine whole-body leucine flux and oxidation. Whole-body protein synthesis was estimated from nonoxidative flux. Muscle protein synthesis rate was determined by measuring [13C]leucine incorporation into muscle samples obtained by needle biopsy. Testosterone increased muscle protein synthesis in all subjects (27% mean increase, P less than ). Leucine oxidation decreased slightly (17% mean decrease, P less than ), but whole-body protein synthesis did not change significantly. Muscle morphometry showed no significant increase in muscle fiber diameter. These studies suggest that testosterone increases muscle mass by increasing muscle protein synthesis.