Testosterone is a male sex hormone and can be used to treat disorders such as hypogonadism, impotence and delayed puberty which is caused by a lack of this hormone, according to CIGNA.com 35. Replacement testosterone can be administered in several different formats; one way is through testosterone injections 135. A physician or nurse administers the injection every two to four weeks. Testosterone injections are associated with some adverse effects or dangers 35.

Worsening of Sleep Apnea

Sleep apnea is a sleep disorder in which the person stops breathing intermittently during the night. Testosterone injections can make this condition worse, according to MayoClinic.com 235. Sleep apnea can be dangerous and life-threatening; a physician needs to evaluate the patient for this condition.

Increased Red Blood Cells

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Testosterone injections can cause an increase a red blood cell counts in some patients 35. This can be problematic because the extra red blood cells can create an obstruction in a blood vessel and lead to a heart attack or stroke, according to the Palo Alto Medical Foundation 4.

Prostate Changes

Testosterone injections may also increase the size of the prostate gland 35. If a man already has benign prostate hypertrophy, which can cause problems with urination, testosterone injections can make this condition worse, according to the Palo Alto Medical Foundation 345. If a man has prostate cancer, he should not receive testosterone injections because the extra testosterone may cause the cancer to increase in size 35.

Enlarged Breasts

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Some men who receive testosterone injections may develop an increase in breast size 35. This danger typically only occurs in adult men who are being treated for hypogonadism and may persist in some patients, according to Drugs.com.

Testicular Changes

The testicles may become smaller in some men who receive testosterone injections 35. In younger men, the testicles may stop producing sperm or produce fewer sperm which decreases fertility. According to the Palo Alto Medical Foundation, problems with fertility typically resolve after stopping the testosterone injections 345.