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Is sebum a type of hormone

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Sebum

Author: Reviewed and updated by Dr Amanda Oakley Dermatologist, Hamilton, New Zealand; Vanessa Ngan, Staff Writer; and Clare Morrison, Copy Editor, June 2014.

What is sebum?

Sebum is a complex and variable mixture of lipids including:

GlyceridesFree fatty acidsWax estersSqualeneCholesterol estersCholesterol

Sebum is produced by sebaceous glands when they disintegrate. The gland cells last about a week, from formation to discharge. The sebaceous glands produce lipids, triglycerides, which are broken down by bacterial enzymes (lipases) in the sebaceous duct to form smaller compounds, free fatty acids. The oil on the surface of skin is a complex mixture of sebum, lipids (from the surface skin cells), sweat and environmental material.

Acne — often associated with excessive sebum



Sebaceous glands are found over most of the body, although there are few on the hands and feet and none on the palms and soles. Sebaceous glands on the mid-back, forehead and chin are larger and more numerous than elsewhere (up to 400–900 glands per square centimetre). They are also numerous in the ear canal and around the genitals.

The sebaceous gland consists of lobes connected by ducts, which are lined with cells similar to those on the skin surface. Most sebaceous glands open out into the hair follicle. Some free sebaceous glands open directly onto the skin surface. These include Meibomian glands on the eyelids, Tyson glands on the foreskin and Fordyce spots on the upper lip and genitals.

What does sebum normally do?

Sebum has the following functions:

It reduces water loss from the skin surfaceIt protects the skin from infectionby bacteria and fungiIt contributes to body odourIt is colonised by the bacteria Proprionibacterium acnes, which may have a role in immune system regulation

Hormonal control of sebum

Sebum production is under the control of sex hormones (androgens). The most active androgens are testosterone, 5-testosterone (DHT) and 5-androstene-317diol. These hormones and others are made by the sex glands (ovary in females, testis in males) and by the adrenal gland. These glands are in turn under the influence of the pituitary gland, located in the brain.