Male pattern baldness: sebaceous gland hypothesis.
Publication: Cosmetics and Toiletries
Publication Date: 01-JUL-90
Author: Inaba, Masumi ; Inaba, Yoshikata
(Old hypothesis- But does it hold good now?)
Clinical observation of patients treated with subeutaneous tissue shaving as a radical treatment for bromidrosis has led the authors to question what is commonly believed about the hair cycle.(1) Until quite recently, the hair cycle was believed to be divided into three stages, anagen, catagen and telogen. Hair regeneration was considered to start from remnant dermal papilla cells or secondary hair germ located at the lowest portion of telogen follicles (Hair Bulb Theory.(2)
The authors have found indications that the essential hair center is located at the upper isthmal portion of the hair follicle close to the secretory duct opening of the sebaceous gland (Sebaceous Gland Hypothesis).
The hair follicle and sebaceous gland form a unit called the pilosebaceous unit. The sebaceous gland has been believed to function only as an exocrine gland which secretes sebum, a surface lipid that moistens the skin and the hair shaft. The relationship between the hair follicle and the sebaceous gland has been studied extensively. However, most studies focused on the morphological difference between them. Few dealt with the relationship between the two, and much remains unclear.
The authors have suggested that the sebaceous gland functions not only as an exocrine gland, but also as an endocrine gland which constantly acts on and controls the hair bulb through the hormones and enzymes it excretes. Basic aspects of essential hair regeneration such as how the hair follicle is regenerated from the upper isthmal portion, how the new hair is formed, and whether or not the conventional hair cycle theory is sufficient have been questioned. Understanding these aspects is essential if the causative mechanism is to be discovered and an effective treatment developed for male pattern baldness.
According to the sebaceous gland hypothesis, MPB occurs because sebaceous glands enlarge. The enlarged sebaceous gland increases sebum production leading to clogging of pores and malnutrition of hair root and also produce excessive amounts of DHT which exert a suppressive action on the hair root.
On the basis of sebaceous gland hypothesis MPB is caused not only by hereditary factors but also by nutritional factors. The direction for new preventive measures and treatments may lie in reducing sebaceous gland size.