It’s easy to demonize dihydrotestosterone (DHT), the male sex steroid hormone identified as the primary cause of androgenetic alopecia (AGA). However, testosterone and DHT are both critical to the maintenance of overall health and vitality.
In this article, we explain what testosterone and DHT are and provide an overview of how these hormones are produced and regulated by the body. We also discuss the role of these androgens in men’s health and what can go wrong when androgen levels are abnormal. Lastly, we review treatments for low testosterone.
For men who are concerned about male pattern hair loss, these discussions provide an important context for why it’s important to develop targeted treatments such as topical finasteride, that can help avoid broad disruption of androgen levels in males.
What are androgens?
Androgens (male sex steroid hormones) serve a number of functions in biological males. They begin the process of sexual development in the womb and help maintain sex-specific traits through adulthood.
Beginning at around 6 weeks gestational age, the testes begin to produce hormones. There are two key types of cells found within the testes: Sertoli and Leydig. Sertoli cells produce a hormone which stops the development of internal female sex organs. Meanwhile, Leydig cells begin to produce testosterone from cholesterol (Hiort, 2013).
Testosterone facilitates both primary and secondary sexual development. Primary development refers to processes relating to sexual function and fertility, such as sperm production and increasing libido (sex drive).
Secondary development refers to changes normally observed during puberty. Examples include the emergence of facial, pubic and axillary hair, a deepening voice and increased height and muscle mass (Nassar & Leslie, 2021).
In addition to these physiological changes, research suggests that testosterone may also influence the development of certain brain tissues. This could account for behavioural differences between males and females, such as increased aggression and competitiveness.
How are testosterone and DHT levels regulated?
Testosterone levels in the blood are maintained by a system called the hypothalamic-pituitary-gonadal axis (HPG axis), which is a type of negative feedback loop. The hypothalamus and pituitary gland (located in the brain) are important control points.
The hypothalamus receives sensory input from other parts of the body and uses gonadotropin-releasing hormone (GnRH) to instruct the pituitary gland to release two additional hormones. These other hormones are follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which travel to their target organs in the male reproductive system.
FSH acts on Sertoli cells to support the growth of healthy sperm while LH facilitates testosterone production in Leydig cells. As rising blood testosterone levels are detected by the hypothalamus, the negative feedback mechanism ensures that secretion of FSH and LH decrease accordingly.
Testosterone synthesis occurs within Leydig cells and begins with molecules of cholesterol. With the help of enzymes, two intermediate molecules, dehydroepiandrosterone (DHEA) and androstenedione are produced (Nassar & Leslie, 2021).
These two androgens are also produced (albeit in smaller quantities) by the adrenal glands located above the kidneys. DHEA and androstenedione can attach to androgen receptors on cells in a similar way to testosterone and DHT. With a few additional chemical reactions, they may also be converted into female sex hormones such as estrogen.
The role of DHEA in physiology and its use as a health supplement is an area of growing research. Experts theorize that DHEA could function as an anti-aging agent, or help treat conditions such as depression and osteoporosis (loss of bone density).
But as with other kinds of hormone replacement therapy, there are potentially serious side effects and a physician’s oversight is necessary when taking this kind of medication.
Once DHEA and androstenedione are converted to testosterone, the 5-alpha reductase enzyme completes testosterone’s transformation into DHT. DHT has a number of important functions depending on a man’s age.
During childhood, DHT levels typically remain low until the age of 6. With the onset of puberty, LH secretion increases along with testosterone and DHT production.
Increased DHT triggers the growth of facial, pubic and axillary hair and ensures the proper development of external sex organs and the prostate gland (Kinter & Anekar, 2021). As a man ages, DHT also plays a role in prostate enlargement and in susceptible individuals, male pattern hair loss.
What causes low testosterone?
Occasionally, testosterone levels may be abnormally low. There are two possible causes of low testosterone (also known as hypogonadism) in men:
- Decreased production of testosterone by the testes, or primary hypogonadism
- Decreased levels of the signaling hormone LH (when LH decreases, this is followed by a drop in testosterone production), also known as secondary hypogonadism.
In men without pre-existing medical conditions, lower levels of testosterone are a natural part of aging. However, the effect of decreased androgens may be more noticeable after the age of 40.
Certain medical conditions such as obesity, kidney disease, diabetes or disorders of the hypothalamus or pituitary gland may also contribute to lower testosterone levels (Petering & Brooks, 2017).
What are the signs of low testosterone?
Signs and symptoms of low testosterone include:
- Gynecomastia (breast enlargement) and breast tenderness
- Erectile dysfunction
- Changes in body composition (increased body fat and/or decreased muscle mass)
- Hot flashes, sweats
- Changes to body hair, hair loss
- Osteoporosis (decreased bone density)
- Decreased libido
- Depression or depressed mood
- Fatigue and decreased energy
Low testosterone is diagnosed with a blood test and a physician’s confirmation of the presence of at least one of the above signs and symptoms.
Thresholds for low testosterone vary regionally. A total testosterone measurement of less than 8 nmol/L (Canada) or 300 ng/dL (U.S.) is generally required. Blood tests for low testosterone are typically done in the morning.
Before a testosterone blood test, it is important for men to refrain from vigorous exercise and/or sexual intercourse for 12 hours prior, as these activities can temporarily increase testosterone levels.
How to treat low testosterone
Once low testosterone and related symptoms are confirmed by a physician, there are a number of treatment options. Hormone replacement therapy (HRT) using synthetic testosterone (available as a patch, pill, gel, nasal spray or intramuscular injection) may be considered.
However, use of this kind of medication carries certain risks and must be overseen by a physician experienced in testosterone replacement and men’s health. Side effects are dependent upon dosage and formulation and need to be closely monitored.
Complete blood count and prostate specific antigen (PSA) monitoring, as well as regular digital rectal examinations and blood pressure checks are essential when using testosterone replacement.
Alternatives to hormone replacement therapy
If erectile dysfunction is the main concern, testosterone therapy may not be necessary or appropriate. Instead, a phosphodiesterase-5 inhibitor such as sildenafil or tadalafil, could be trialed (Petering & Brooks, 2017).
Treating erectile dysfunction separately with a specific medication may help avoid the potential side effects of HRT that could include increased risk of cardiovascular disease, polycythemia (elevated red blood cell count and blood clotting risk) and/or risk of prostate cancer. You should talk to a physician about whether HRT is right for you.
Vitamin D and minerals such as zinc and magnesium may also be beneficial. Other herbal supplements containing ingredients like fenugreek and ashwagandha have also been shown to have a positive effect on sexual wellness. Research on the long term benefits and side effects (where applicable) of these natural alternatives is ongoing.
Role of testosterone and DHT in men's health: Takeaway
Although it plays a role in pattern hair loss, DHT is one of the building blocks of men’s health and vitality. Because age is generally a factor in the development of low testosterone, it’s important to stay on top of any unusual changes to your health or new symptoms and communicate these regularly to a physician.