Background

March 13, 2013

Human Aging and Hair Loss

Human hair is at its healthiest and most attractive throughout adolescence due to the length of time the body devotes to supporting hair growth. Throughout youth and adolescence single hairs can grow for up to 7 years, with short resting phases that last as little as 4 months. At about 35 years of age, hair growth rates begin to change, resulting in reduced density and thinner overall appearance of hair. With each new growth cycle, the length of time devoted to growing hair is reduced, resulting in shorter, thinner hairs. Additionally, the amount of time spent in the resting phase grows longer, resulting in longer periods of time between when a hair falls out and when a new one grows back. Over time these changes can add up to a significant reduction in overall hair density and appearance.

Changes in hair color also begin to appear at this time, as pigment-producing melanocytes begin to gradually die out. Over time the hairs begin to lose their luster and color, slowly turning grey before becoming totally white.

Accelerated Hair Loss

While gradual hair loss is a normal part of human aging, for many people, excessive hair loss, or balding, is a significant source of anxiety. Hair loss can be roughly divided into two categories — temporary and permanent. Temporary hair loss, which is often caused by excessive stress, poor diet, hormonal imbalance, and endocrine dysfunction, can often be restored within six months to two years after eliminating the underlying cause(s). Permanent hair loss is caused by genetics and is considered incurable.

Male Pattern Hair Loss

Male-pattern hair loss is linked to androgens — sex steroid hormones synthesized from cholesterol in the testes, ovaries and adrenal glands. The primary androgens — testosterone, pregnenolone, androstenedione and DHEA (dehydroepiandrosterone) — normally regulate male and female sexual development and behavior by binding to receptors on target cells throughout the body.

 

hair loss chart

 

Researchers have identified another androgen, dihydrotestosterone (DHT), as the main culprit in male pattern baldness. DHT, which is synthesized from testosterone by the enzyme 5alpha-reductase, binds to receptors in the hair follicle, causing the hair roots to shrink, or “miniaturize.” DHT has also been shown to shorten the growing phase (anagen) of hairs from up to 5 years down to as little as 2 months.

Over time, DHT’s miniaturizing effects can transform large adult hairs into finer, vellus hairs, only about 10% as wide as normal hair and barely an inch long, leading to the “peach fuzz” appearance commonly seen in early stage balding. At this stage, if the effects of DHT aren’t reversed or halted in time, the hair follicles will continue to miniaturize until they eventually die out, leading to complete baldness in the affected area.

In 1998 researchers discovered that men genetically prone to male pattern baldness have significantly higher numbers of androgen receptors in the hair follicles located across the forehead and scalp — exactly those areas where hair loss first appears in androgenic alopecia. Additional research has shown that these androgen-sensitive follicles also have significantly higher levels of 5alpha-reductase (1.5 to 3 times higher) and DHT than hair follicles from other areas of the scalp.

Female Pattern Hair Loss

Hair loss isn’t exclusively a male problem — approximately 50% of all women over the age of 50 experience a similar condition, referred to as female androgenic alopecia. Symptoms in women are generally less severe than in men, resulting in an overall thinning of hairs across the top of the head, and the gradual loss of hairs down the center part-line of the scalp.

 

female hair loss

 

The reason women experience milder symptoms is due to hormonal differences —  women produce significantly lower amounts of testosterone than men (about 95% less on average). Women also produce lower levels — about 60 percent less than men — of the enzyme 5α-reductase that converts testosterone into DHT. Additionally, women produce higher levels of another enzyme, aromatase (estrogen synthase), that converts testosterone into the female hormone, estradiol. While males also produce small amounts of aromatase, research has shown that aromatase levels in the frontal and rear scalp follicles in women are 4 to 6 times higher than in men, which is why women rarely lose hair in these areas.

Healthy Follicles for Healthy Hair

Hair follicles are among the most active and fastest growing structures in the body. Human hairs are produced by follicles — specialized organs that cover the entire body, with the exception of the palms and soles of the feet. Follicles are composed of three major structures — the dermal papilla, hair matrix, and hair shaft. (Fig 1).

 

hair growth

 

The dermal papilla, a pear-shaped structure located at the base of the hair follicle, is comprised of connective tissues and a capillary loop containing tiny blood vessels that provide the nutrients required for hair growth. The papilla is surrounded by the matrix — a bulb-shaped collection of specialized epithelial cells that produce a protein, keratin, that actually forms the hair fiber. The matrix also contains melanocytes, specialized pigment cells that infuse the growing hair shaft with melanin, the compound that gives otherwise transparent hair its natural coloring.

Different types of melanin produce different colors — yellow, rust, brown, and black — that combine to produced a wide variety of hair colors, ranging from blond to brown to pitch black. Red hair is the result of another type of coloring agent, the iron-containing pigment called trichosiderin.

Mature human hair cycles through three distinct phases — growth, transition and rest – that are collectively referred to as the hair cycle.

1. Growth (Anagen) Phase: Each hair cycle begins with the growth (or anagen) phase. This is marked by rapid cell division in the hair matrix that builds up layers of keratin to form a single hair shaft that grows out from the follicle at a rate of up to one inch per month. This growth phase typically last for between two to six years. At any given time about ninety percent of all scalp hairs are in the active growing phase.

2. Transitional (Catagen) Phase: At the end of the growth (anagen) phase, hair growth ceases as the follicle enters the transition (or catagen) phase. During the catagen phase, the hair matrix cells die off as the follicle and bulb begin to shrink. Over time, continued shrinkage (miniaturization) pinches off the lower hair bulb, cutting off access to blood vessels, restricting circulation necessary for hair growth. At any given time, one to two percent of all hair follicles are in this transition phase, which usually lasts one to two weeks.

3. Resting (Telogen) Phase: The final stage of the hair cycle is the resting (or telogen) phase. During this phase, mature hairs reside in the follicle for five to six weeks before falling out. Approximately 10 percent of all hairs are in the resting phase at any time, accounting for the normal shedding of between thirty and fifty hairs each day.

After shedding the hair shaft, the follicle begins a new cycle of hair growth, marked by the swelling of the dermal papilla and the formation of a new capillary loop. As blood vessels reattach to the papilla, they grow and expand four-fold to provide the hair matrix with the nutrients necessary for growing new hair.

The entire process — growth, transition and rest — makes up one complete hair cycle. Each hair follicle is limited to the number of hair cycles that can be completed — estimated to between 20 and 25 cycles — before reverting to vellus hairs (peach fuzz) and eventually disappearing.

Treating Hair Loss

An ideal solution for treating hair loss would promote new hair growth while extending the anagen (growing) phase, lengthening the catagen (transitional) phase and shortening the telogen (resting) phase.

In western medicine the two most widely used medical treatments for androgenic alopecia — Propecia® and Rogaine® — offer partial solutions by addressing hair loss in two completely different ways. Propecia primarily works to halt hair loss by blocking the production of the follicle-damaging hormone, DHT, while Rogaine aims to support hair growth by increasing blood flow to the hair roots.

Blocking Production of DHT

Propecia (Finasteride), is an oral prescription drug first marketed as Proscar® for the treatment of enlarged prostate (BPH or Benign Prostatic Hyperplasia). Proscar (5 mg finasteride) lowers DHT levels by preventing the enzyme, 5alpha-reductase, from converting testosterone into DHT. After Proscar was approved for BPH, researchers noted that men taking the drug were showing signs of hair regrowth. This led the approval of a lower dose (finasteride 1 mg) by the FDA in 1997 and marketed as Propecia™ for the treatment of androgenic alopecia in men.

Following its introduction, Propecia was shown to be highly effective for decreasing DHT concentrations in the blood (up to 70%), and the scalp (up to 60%) to reverse DHT-related hair loss of the vertex (at top of head) and anterior mid-scalp area.

Unfortunately, in addition to being in hair follicles, 5α-reductase is abundant in the prostate and seminal vesicles, where it plays a vital role in the healthy development and maintenance of normal physiological functions. Reduction of DHT in these organs has been linked to unwanted side effects in men, including decreased libido, sexual dysfunction, and a reduction of mature sperm count. Additionally, women cannot use Propecia, women who are or may be pregnant are explicitly warned to not to even handle crushed or broken Propecia tablets, since the active ingredient may cause abnormalities of a male baby’s sex organs.

Increasing Blood Flow

Minoxidil was originally developed as an oral drug to treat hypertension, based on its ability to relax vascular smooth muscles and produce peripheral vasodilation. By directly stimulating circulation to the hair follicles, Minoxidil was found to extend hair and redirect resting hair follicles into new growth. Animal experiments suggest that Minoxidil works, in part, by increasing vascular endothelial growth factor (VEGF) to promote hair growth and reactivate dormant hair follicles.

When taken orally to restore hair, minoxidil was also found to have a number of side effects, including unwanted hair growth in women (hirsutism). Most of these side effects were averted when a topical form, Rogaine, was approved for use as an external-use hair-restorer in 1988. Minoxidil has been shown to perform well in preventing hair loss (80%), but less than 20% of patients with androgenetic alopecia experience actual hair growth. Additionally, if treatment is stopped the hair growth benefits disappear and the scalp reverts back to its untreated state within three months.

A Better Approach to Hair Loss

In Traditional Chinese Medicine (TCM), hair loss is a condition that can best be treated with a two-pronged approach that can balance both the “surface” and “root” levels of the problem. In this case, the “surface” level is the hair and scalp, and the “root” level is the general body health and constitution.