Menopause is characterized by the cessation of ovarian function and a significant reduction in sex hormone production. These hormonal shifts influence various tissues, including the skin and hair follicles. The resulting changes in the hair growth cycle can lead to noticeable differences in hair density, texture, and distribution across the body. Understanding these physiological responses requires examining how the new hormonal balance impacts hair follicle activity.
The Relationship Between Menopause and Axillary Hair Growth
The common experience after menopause is a notable reduction in underarm, or axillary, hair growth. For most people, the hair does not cease growing entirely but becomes significantly sparser and finer. The terminal hairs that were thick and dark often become lighter and less dense. The growth rate also slows down considerably, decreasing the frequency required for shaving or trimming. In older postmenopausal women, hair follicles may enter a prolonged resting phase, or telogen, which makes the hair appear to have stopped growing.
The Role of Hormones in Hair Follicle Activity
Hair growth is regulated by a balance between estrogens and androgens. Estrogen supports hair growth by prolonging the anagen, or active growth, phase of the hair cycle. The sharp decline in estrogen following menopause removes this growth-promoting support from the follicles. Although androgen levels also decrease with age, their decline is more gradual than the drop in estrogen. This shift creates a state of relative androgen dominance, which causes the anagen phase to shorten dramatically. This mechanism leads to the production of thinner, lighter, and shorter hairs, explaining the miniaturization of underarm hair.
How Hair Changes Differ Across the Body
The postmenopausal hormonal environment does not affect all body areas uniformly, as hair follicles exhibit differential sensitivity to androgens. The thinning of axillary and pubic hair contrasts sharply with changes on the face. Follicles on the upper lip and chin are highly sensitive to androgen stimulation. In these facial areas, relative androgen dominance can stimulate vellus hairs—the fine “peach fuzz”—to convert into thick, dark terminal hairs. This results in unwanted facial hair growth, while scalp follicles often respond by shrinking, leading to diffuse thinning or female pattern hair loss.
Individual Variations in Postmenopausal Hair Growth
The degree to which axillary hair thins or slows varies significantly among individuals. Genetic predisposition plays a substantial role in determining how sensitive hair follicles are to hormonal fluctuations. Ethnicity also influences the natural distribution and density of body hair, affecting the starting point of postmenopausal changes. Factors beyond reproductive hormones influence the outcome, including overall health status and underlying medical conditions like thyroid disorders. Certain medications may also affect circulating hormones or their interaction with hair follicles, leading to further individual variation.