Low testosterone levels, or “low T,” can be caused by a wide variety of medical conditions or by the use of some drugs.
After age 30, most men experience a gradual drop in testosterone.
However, this decrease rarely results in a “low T” level that’s substantially lower than what’s considered normal for a middle-aged or older man.
A variety of medical conditions, however, can cause significantly lower-than-normal testosterone levels in boys and men.
- Autoimmune diseases
- Chronic liver or kidney disease
- Chronic obstructive lung disease
- Genetic causes
- Heart failure
- Infections (such as mumps)
- Injury to the testicles
- Metabolic disorders
- Prolactinoma (prolactin-secreting tumor) in the pituitary gland
- Testicular cancer or treatment for testicular cancer
- Type 2 diabetes
Some drugs are also associated with low testosterone levels, including:
- Chemotherapy drugs used to treat cancer
- Corticosteroids (sometimes called glucocorticoids)
Sometimes the cause of low testosterone in a man is unknown, and many men have several different causes.
Obesity, which is epidemic in the United States as well as a growing problem in other parts of the world, has been observed to have a lowering effect on testosterone levels in men.
Obesity is defined as a Body Mass Index (BMI) higher than 30 kg/m2.
A study published in the Journal of Clinical Endocrinology & Metabolism in 2007 found that a 4- to 5-kg/m2 increase in BMI is associated with a drop in testosterone comparable to that associated with 10 years of aging.
A 2008 study in the same journal found that a large waist or an increase in waist circumference over time is an important contributor to low T — even more important than age.
The good news is that weight loss is associated with an increase in testosterone levels.
A 2004 study in the journal Diabetes, Obesity and Metabolism found that men who lost weight quickly over 9 weeks on a very-low-calorie diet and maintained their weight loss for 12 months had sustained increases in testosterone.
Studies of men who have had bariatric (weight-loss) surgery have also shown that significant weight loss leads to significant increases in testosterone levels.
But even moderate weight loss can help: In research presented at the 2012 annual meeting of the Endocrine Society, middle-aged obese men who lost modest weight while following a year-long diet and exercise program had modest increases in testosterone level.
Low Testosterone in Women
While abnormally low testosterone levels in women get less attention than low-T levels in men, they can occur and are caused by a variety of factors, including:
- Adrenal insufficiency
- Dysfunction in the interactions among the hypothalamus, pituitary gland, and adrenal glands
- Hypopituitarism (reduced secretion of hormones from the pituitary gland)
- Hysterectomy (surgical removal of the uterus)
- Premature ovarian failure
- Surgical removal of the ovaries
- Use of combination oral contraceptive pills
Women also experience a gradual lowering of testosterone production in the years leading up to menopause.