Puberty is a period of dramatic hormonal changes. In boys, testosterone levels rise, and some testosterone is converted into dihydrotestosterone (DHT). DHT can cause hair follicles to shrink, leading to thinning hair or even the early signs of androgenetic alopecia (male-pattern hair loss). In girls, hormonal imbalance during puberty can lead to increased hair shedding, an oily scalp or excessive hair growth in unusual areas.

During pregnancy, oestrogen levels rise significantly, which can keep hair in the growth phase (anagen) for longer. This makes hair appear fuller and thicker. After childbirth, however, oestrogen levels fall, often leading to postpartum hair shedding (telogen effluvium). This condition is temporary, but it can be very stressful, as women may notice substantial hair loss for several months after giving birth.

Menopause is another period of major hormonal changes. Oestrogen and progesterone levels decrease, while androgen levels (male hormones) may remain relatively high. This shift can contribute to hair thinning or female-pattern hair loss. Hair may also become drier and more fragile as sebum production decreases.

The thyroid gland produces hormones that regulate metabolism and also influence hair health. Hypothyroidism (an underactive thyroid) can cause thinning and brittle hair, while hyperthyroidism (an overactive thyroid) can lead to hair loss. Both conditions can also leave hair looking dull and lifeless. Nutrient deficiencies: A lack of essential nutrients, such as vitamins and minerals, may slow hair growth. B vitamins, zinc, iron and protein are particularly important.


Genetically Shortened Hair Growth Phase

Telogen effluvium: One of the most common ways stress affects hair is through a condition called telogen effluvium. In a normal hair cycle, most hairs are in the anagen (growth) phase, while a smaller proportion are in the telogen (resting) phase, when hair stops growing and prepares to shed. Chronic stress can cause a large number of hairs to move into the telogen phase around the same time. The result is sudden, noticeable hair shedding that may appear several weeks to months after a stressful event.

Shortening of the growth phase (anagen phase): Stress can also shorten the hair growth phase, meaning that hair may not reach its maximum length before entering the telogen phase prematurely. This can contribute to thinning because fewer hairs remain in the active growth phase.

Hormones and stress: Stress affects hormone production, particularly cortisol, known as the “stress hormone”. Elevated cortisol levels can disrupt the body’s normal hormonal balance and may negatively affect hair follicles. Stress may also influence androgen levels, which are associated with hair loss, especially in people prone to androgenetic alopecia.

Autoimmune reactions: In some cases, stress may trigger or aggravate autoimmune conditions such as alopecia areata, in which the immune system attacks hair follicles, causing sudden hair loss in small patches.