Hair Loss: Common Causes and Treatment

Life cycle of hair

The hair cycle is composed of four primary phases: anagen, catagen, telogen, and exogen. Anagen is a highly mitotic phase characterized by the production of a hair shaft from the hair follicle, whereas catagen and telogen describe regression and the resting phase of the follicle, respectively, ultimately resulting in hair shedding. While 9% of hair follicles reside in telogen at any time, a variety of factors promote anagen to telogen transition, including inflammation, hormones, stress, nutritional deficiency, poor sleep quality, and cellular division inhibiting medication. Conversely, increased blood flow, direct stimulation of the hair follicle, and growth factors promote telogen to anagen transition and subsequent hair growth.

While most individuals have about 100,000 scalp hairs at any time, normal shedding occurs at a rate of 100 to 150 telogen hairs per day . As some hairs reside in the anagen phase while others are resting or shedding, the density and total hair strand number remains relatively stable in healthy conditions.

Factors Increasing Telogen Transition and Hair Loss

Inflammation

Inflammation fosters anagen to telogen transition and has been associated with the progression of alopecia. Inflammation has been suggested to mediate a variety of hair loss subtypes, including stress-induced hair loss, alopecia areata, and male- and female-pattern hair loss, also known as androgenic alopecia. Each of these alopecia subtypes are associated with a decreased anagen to telogen ratio.

Hormones

A variety of hormones have been shown to impact the hair cycle and mediate hair growth, including thyroid hormones, dihydrotestosterone (DHT), estrogen and testosterone.

Thyroid Hormone Hypo- and hyperthyroidism can cause reversible, diffuse hair loss and can promote premature transition from anagen to telogen, potentially resulting in telogen effluvium.

Dihydrotestosterone: Dihydrotestosterone (DHT) is an androgenic steroid hormone produced via the action of 5-alpha-reductase type 2, which converts testosterone to DHT at target tissues. While androgens increase hair follicle size in androgen-dependent locations, they can result in miniaturization of scalp follicles later in life. DHT is a pure androgen, as it cannot be converted to estrogen. In addition to the sexual development of males, DHT promotes male-pattern hair loss. Upon binding to androgen receptors in the hair follicle, DHT promotes the shortening of the anagen phase and elongation of the telogen phase , resulting in enhanced apoptosis of hair cells and thus hair loss.

Stress

The association of stress and hair loss has been widely documented. Substance P-dependent inflammatory pathways may mediate stress-induced hair loss.

Nutritional Deficiencies

 Proper nutrition is essential for anagen and telogen balance, and caloric or nutritional deficiency can negatively impact hair structure, growth, and pigmentation. Furthermore, hair loss can occur following rapid weight loss or reduced protein intake, and diffuse alopecia may be a presenting sign of nutritional deficiency.

Studies have found associations between nutritional deficiency and a variety of types of hair loss, . A variety of nutritional components have been evaluated for their effect on hair structure and growth, including a variety of vitamins and minerals, in addition to fatty acids and protein. There remains continued uncertainty regarding the value of nutritional supplementation for hair loss, especially among non-deficient individuals, and the over-supplementation of some nutrients may increase toxicity and even contribute to hair loss.

Poor Sleep

Poor sleep has been associated with increased risk and severity of alopecia subtypes. Many studies have shown an increased correlation  between  reduced sleep quality and alopecia.

Factors Increasing Telogen to Anagen Transition and Hair Growth

There are a variety of factors that conversely mediate telogen to anagen transition and thereby support hair growth, including increased blood flow, direct stimulation of the hair follicle, and growth factors.

Increased Blood Flow

Developing hair follicles are surrounded by deep dermal vascular plexuses. Associated blood vessels function to supply nutrients to the developing follicle and foster waste elimination. As such, proper blood supply is necessary for effective hair follicle growth, further exemplified by the angiogenic properties of the anagen phase.

Scalp Massage: Theoretical benefits of increased blood flow to the hair follicles justifies the assessment of scalp massage on hair parameters. Scientists thereby concluded that a standardized scalp massage and subsequent dermal papilla cellular stretching can increase hair thickness.

Direct Stimulation of the Hair Follicle (Herbs and Phytochemicals)

Scientifically, capsaicin and catehins in coffee are considered a promising natural approach to effectively addressing hair loss stemming from increased  DHT levels.

Rosemary oil is a herbal remedy that has been suggested to increase hair growth. Some studies showed comparable results to minoxidil, a first line medication for hair loss treatment.

Proanthocyanins have shown promising results for hair growth in the literature. A study conducted on mouse hair follicle cells found that proanthocyanins extracted from grape seeds caused a 230% increase in proliferation compared to the control vehicle.

Garlic is perfect antioxidant approach. It is also a source of various enzymes, vitamins,  amino acids, flavonoids and sulfur making it helpful for hair growth.