The observation that older men grow hair in unexpected places while simultaneously losing it on their scalp is a biological reality. This paradox is explained by the complex, localized interaction between male hormones and individual hair follicles as a man ages. It is a consequence of differing, genetically programmed sensitivities across the body, not a simple trade-off. Understanding this change requires looking at the hormonal signals that regulate the hair growth cycle.
The Role of Hormones in Hair Change
The primary drivers behind hair changes in men are androgens, a class of hormones that includes testosterone and its more potent derivative, dihydrotestosterone (DHT). DHT is produced when the enzyme 5-alpha reductase converts testosterone in specific tissues, including the skin and hair follicles. Although overall testosterone levels may decline slightly with age, the long-term exposure and localized effects of these hormones continue to influence hair growth cycles.
Hair follicles across the body are not uniform in their reaction to DHT; their sensitivity is determined by genetics. Hair is categorized into two types: vellus hair, which is fine, short, and lightly pigmented, and terminal hair, which is thick, long, and darker. Androgens trigger the conversion of vellus hair to terminal hair during puberty, but the continued presence of DHT in adulthood causes differing effects in various body regions.
The key mechanism is not necessarily a change in the total amount of circulating hormones, but a change in the sensitivity of the androgen receptors within the follicle itself. This localized sensitivity determines whether a follicle is stimulated to grow longer and thicker, or signaled to shrink. A high concentration of DHT-sensitive receptors in a follicle can lead to two entirely different outcomes depending on the follicle’s location.
Specific Areas of Increased Hair Growth
The perception that men get “hairier” as they age is largely due to the transformation of hair in specific facial and sensory areas. In the nose, ears, and eyebrows, hair follicles tend to become progressively more sensitive to androgen stimulation over time. This increased sensitivity leads to the conversion of vellus hairs into thicker, more noticeable terminal hairs.
This change is primarily caused by a prolonged anagen, or growth, phase in these specific follicles. While the anagen phase for scalp hair lasts for years, the growth phase for ear and nose hair is normally short. With advancing age, follicles in the ears (particularly on the tragus) and inside the nostrils respond to continuous hormonal exposure by remaining in the active growth phase longer, resulting in longer and coarser strands.
The eyebrows also thicken and lengthen with age due to this prolonged anagen phase. Variability in the increase of body hair, such as on the back or chest, is highly dependent on an individual’s genetic predisposition and the density of androgen receptors in those areas. For some men, the continued presence of androgens promotes further terminal hair development on the trunk.
Understanding Male Pattern Hair Loss
The simultaneous process of hair loss on the scalp, known as Androgenetic Alopecia, represents the opposite reaction to the same hormonal stimulus. In men genetically predisposed to this condition, the hair follicles on the crown, temples, and frontal scalp are hypersensitive to DHT. Unlike the follicles in the ears and nose, this sensitivity causes a destructive process.
When DHT binds to the androgen receptors in these susceptible scalp follicles, it triggers a cascade that progressively shortens the anagen phase. The hair growth cycle is dramatically truncated from a normal duration of several years to just a few months. This process is known as follicular miniaturization, where the terminal hair follicles gradually shrink.
With each successive cycle, the hair shaft produced becomes thinner, finer, and shorter, eventually resembling the vellus hair seen in childhood. This progressive conversion of thick terminal hairs into barely visible vellus-like hairs is the hallmark of pattern hair loss. This reaction contrasts with the growth response seen in the beard, nose, and ear follicles, demonstrating that the effect of androgens is highly localized and genetically determined.