How Your DNA and Hormones Shape Hair Growth and Loss

Are you suffering from hair loss? Hair fall is a common problem for both men and women. And it is on of the most visible markers of individuality, and much of its character is written into our DNA. The hair cycle and hair follicle structure are completely dependent on various hormones.

As per National Library of Medicine, ‘Androgens, such as testosterone; dihydrotestosterone; and their prohormones, dehydroepiandrosterone sulfate and androstenedione—are the key factors in terminal hair growth.’

Genetics determine the baseline qualities of hair, its thickness, density, curl pattern, and growth rate. For example, some people inherit naturally coarse, voluminous strands, while others have fine, silky hair. These traits are passed down through gene variants that influence proteins such as keratin and collagen, which provide strength and elasticity.

Genetics also govern the hair growth cycle, which includes the anagen (growth), catagen (transition), and telogen (resting) phases. The length of the anagen phase varies from person to person, explaining why some individuals can grow waist‑length hair while others struggle to grow beyond shoulder length.

How Is Hormones and Hair Health Related?

While genetics set the foundation, hormones act as powerful regulators that can either enhance or disrupt hair health. Hormones influence the timing and balance of the hair cycle, determining whether follicles remain in the growth phase or shift prematurely into shedding.

Key hormonal players include:

1.      Androgens (testosterone and dihydrotestosterone, or DHT): These hormones can shrink hair follicles, leading to thinner strands and eventual hair loss. Elevated sensitivity to DHT is a hallmark of male and female pattern baldness.

2.      Estrogen and progesterone: These hormones often promote fuller, healthier hair. During pregnancy, when estrogen levels rise, many women experience thicker hair. However, postpartum hormonal shifts can trigger temporary shedding.

3.      Thyroid hormones: Both hyperthyroidism and hypothyroidism can disrupt hair growth, causing brittleness, thinning, or excessive shedding.

4.      Cortisol (stress hormone): Chronic stress elevates cortisol, which can push follicles into the resting phase, leading to diffuse hair loss.

Hormonal fluctuations across life stages—puberty, pregnancy, menopause, or aging—often manifest in noticeable changes in hair texture and density.

‘The hair shaft is divided into three layers: the cuticle, the cortex, and the medulla. The medulla is the outermost part of the hair which is visible above the skin. It is surrounded by a protective layer called the root sheath. The root sheath consists of two strata: the inner and the outer’, according to National Library of Medicine.

Genetics and Hormones

The relationship between genetics and hormones is dynamic. Genetics establish the potential of hair, while hormones determine how that potential is expressed.

For instance, someone genetically predisposed to baldness may not notice significant thinning until hormonal changes, such as increased androgen activity, trigger the process.

Can We Change Hormonal Imbalance?

Understanding the genetic and hormonal influences on hair health helps explain why treatments vary in effectiveness. Genetic factors are largely unchangeable, but hormonal imbalances can often be managed. For example:  

• Medical treatments such as anti‑androgen therapies or thyroid regulation can restore balance and improve hair growth.

• Lifestyle interventions—stress management, nutrition, and sleep—help regulate cortisol and other hormones.

• Preventive care like gentle handling, scalp health maintenance, and minimizing chemical damage can maximize the genetic potential of hair.

Hair health is not dictated by a single factor but by the conversation between genes and hormones.

Disclaimer: This content is for general informational purposes only and should not replace professional medical advice. Always consult a qualified healthcare provider with any questions about your health or treatment options.