Eyebrows play an important role in facial expression and aesthetics. The growth and thickness of eyebrows are determined by hormones, namely testosterone. Here’s a quick overview of how hormones influence eyebrow growth:
Testosterone is the primary hormone that stimulates eyebrow growth. It triggers and maintains the growth phase (anagen) of eyebrow hair follicles. Higher levels of testosterone lead to thicker, darker, and fuller eyebrows.
Testosterone levels are much higher in males after puberty, which is why men tend to have bushier, more prominent eyebrows than women. Fluctuating testosterone in women can also impact eyebrow fullness.
While testosterone is the main driver, other hormones can also influence eyebrow growth:
- Estrogen – Helps stimulate follicle growth. Low estrogen can cause thin eyebrows.
- Growth Hormone – Stimulates hair growth and eyebrow thickness.
- Thyroid Hormones – Thyroid disorders can cause thinning of the outer third of the eyebrow.
The interplay between these hormones regulates the hair growth cycle and determines the thickness and fullness of eyebrows.
Eyebrow Growth Cycle
Like scalp hair, eyebrows go through three phases of growth:
- Anagen (Growth Phase) – Can last 2-4 years for eyebrows. This is when active growth occurs.
- Catagen (Transition Phase) – Lasts 2-3 weeks. The hair follicle detaches from the blood supply and stops growing.
- Telogen (Resting Phase) – Eyebrow hair rests for 2-3 months before shedding. New hair then enters anagen phase.
Hormones like testosterone regulate the hair follicle’s transition between these phases. Higher testosterone prolongs anagen, leading to thicker, faster-growing eyebrows.
Causes of Thinning or Loss of Eyebrows
If eyebrows seem excessively thin or patchy, it may be due to:
- Hormonal changes – Low testosterone, thyroid disorders
- Aging – Decline in growth hormones
- Medical treatments – Chemotherapy, radiation
- Autoimmune diseases – Alopecia areata
- Infections, stress, nutritional deficiency
- Excessive plucking, waxing, threading of eyebrows
Consult a dermatologist if eyebrow hair loss is a concern. Blood tests can check for hormonal imbalances or health conditions leading to thinning eyebrows.
Treatment for Thin Eyebrows
If a hormonal imbalance is causing thin eyebrows, treatment may include:
- Hormone replacement therapy – Testosterone or estrogen supplements
- Medications that promote hair growth – Minoxidil, bimatoprost
- Platelet-rich plasma (PRP) therapy
- Hair transplants for permanent fuller brows
Proper diagnosis and management of any underlying medical condition can help restore eyebrow growth. Temporary methods like eyebrow tattoos, microblading, or tinted powders can also create the look of fuller eyebrows.
Testosterone is the primary hormone that controls eyebrow growth and thickness. Other hormones like estrogen and growth hormone also play a role. Hormonal imbalances, aging, medications, and health conditions can lead to thinning eyebrows. Treatment aims to address the underlying cause and may include hormone therapy, growth promoting drugs, or cosmetic procedures to achieve fuller-looking eyebrows.