Introduction - puberty Introduction - adolescence Stages of puberty Commencement of puberty Physiological skin changes in puberty Changes in hair distribution Changes in the microbiome Skin conditions and puberty Precocious puberty Delayed puberty
Puberty refers to the period of life during which an individual undergoes physical development and sexual maturation to acquire the ability to reproduce. During puberty, the individual also undergoes psychosocial changes and development of secondary sexual characteristics. These are:
Adolescence is defined by the transitional stage of physical maturation and psychosocial development, generally occurring from puberty to adulthood. Although the period of adolescence is closely associated with teenage years, it is difficult to define a precise time interval for this stage of life. Adolescents experience several types of maturation:
Puberty is defined by:
Sexual maturity can be classified into stages according to the Tanner staging system—a scale of physical development based on primary and secondary sexual characteristics, such as the size of breasts and genitalia, testicular volume, and pubic and axillary hair (Tables 1-3).
Table 1: Sexual maturity rating of pubic hair in boys [2] |
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Stage 1 |
Prepubertal with no pubic hair |
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Stage 2 |
Sparse, straight pubic hair along the base of the penis |
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Stage 3 |
Hair is darker and coarser, extending over mid-pubis |
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Stage 4 |
Pubic hair adult-like in appearance but does not extend to thighs |
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Stage 5 |
Hair is adult-like in appearance, extending to medial surface of thighs |
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Table 2: Sexual maturity rating of pubic hair in girls [2] |
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|---|---|---|
Stage 1 |
Prepubertal with no pubic hair |
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Stage 2 |
Sparse, straight hair along lateral vulva |
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Stage 3 |
Hair is darker and coarser, extending over the mid-pubis |
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Stage 4 |
Hair is adult-like in appearance, but does not extend to thighs |
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Stage 5 |
Hair is adult-like in appearance, extending to medial surface of thighs |
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Table 3: Sexual maturity rating of breast development in girls [2] |
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|---|---|---|
Stage 1 |
Prepubertal, no palpable breast tissue |
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Stage 2 |
Breast bud, elevation of the papilla, enlargement of areolar diameter |
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Stage 3 |
Enlargement of the breast, without separation of areolar contour from breast |
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Stage 4 |
Areola and papilla project above the breast, forming a secondary mound |
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Stage 5 |
Recession of the areola to match the contour of the breast; the papilla projects beyond the contour of the areola and breast |
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The age at which puberty occurs is highly variable.
In males, based on Tanner's data, genitalia began to enlarge in 95% of boys from the age of 9.5–13.5 years (mean 11.6 ± 0.9 years) [3]. Functional puberty, defined by the ability to ejaculate, occurs between ages 13–17 years (mean 14.9 ± 1.1 years).
In females, the development of breast buds at thelarche is one of the earliest signs of puberty. This occurs in white North American girls at age 9.96 ± 1.82 years, and in African American girls at 8.87 ± 1.93 years. Pubic hair growth begins at around age 9 as a result of adrenarche, which is dependent on pituitary ACTH production. The average age at menarche is 13, with a range of 10–16.5 years.
Puberty occurs when gonadotrophin-releasing hormone (GnRH) is released from the hypothalamus in the brain. As a result, the pituitary gland (also within the brain) is stimulated to release other hormones (FSH and LH) that act on the sexual organs to produce the hormones oestrogen and testosterone.
Testosterone is responsible for several skin changes at puberty. It increases sebum production (oil) and armpit sweating from apoeccrine sweat glands. It is also the cause for pubic and axillary hair growth.
Menstrual cycle hormonal fluctuations also give rise to cutaneous changes, including premenstrual exacerbation of pre-existing skin disorders such as psoriasis, atopic eczema, and lupus erythematosus.
After birth, hair is divided into two main types: vellus hair and terminal hair.
Prenatal lanugo hair, which is characteristically soft, fine, unmedullated, and usually pigmented [3], is not usually present after birth.
Before puberty, terminal hair is limited to the scalp, eyelashes, and eyebrows. Following puberty, under the influence of androgens—mainly testosterone—terminal hair develops from vellus hair to give rise to secondary hair growth in armpits and pubic regions [3].
The microbiome refers to microorganisms that are normally resident on our skin. One study observed greater variation in the microbiome of Tanner stage 1 children compared to Tanner stage 5 individuals. Predominant organisms are:
The Stage 5 bacteria are lipophilic (oil-loving) and are found in sebaceous skin regions such as the scalp, face and upper trunk [4]. The increase in these lipophilic bacteria is likely due to higher content of epidermal lipids from sebum. The colonisation of skin by lipophilic bacteria reduces the skin pH, which in turn, inhibits growth of the pathogens staphylococci and streptococci.
The increased density and thickness of hair growth and increased apocrine gland activity in puberty may also affect the microbiome.
Rise in androgen levels at puberty can herald the start of genetically programmed familial characteristics. These include:
Congenital melanocytic naevi (brown birthmarks) may increase in size and become more pigmented in puberty. Prominent terminal hairs may form within them. A Becker naevus may appear for the first time. Sebaceous naevi become thicker with a bumpy surface.
Skin disorders that tend to start during adolescence include:
Precocious, or premature (early), puberty is said to occur when pubertal signs are noted in boys before the age of 9, and when they are noted in girls before the age of 8 [5]. Children with precocious puberty should be referred to an endocrinologist for investigation. Treatment depends on the cause.
Precocious puberty follows early activation of the hypothalamo-pituitary-gonadal axis, when it is known as 'true', 'complete' or 'central' puberty. Pseudo-puberty is defined as sex hormone secretion independent of normal control mechanisms.
Precocious puberty can be detrimental to behaviour and psychological development, can reduce height as an adult, and may lead to health risks.
Table 4: Classification of premature puberty [3]. |
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|---|---|
Complete (true puberty) |
False (pseudopuberty) |
Constitutional
Cerebral/neurogenic
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Adrenal lesions
Cushing syndrome/hyperplasia Ovarian tumours Testicular tumours Iatrogenic (sex hormones) Extrapituitary gonadotrophin secreting tumours
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Delayed puberty is defined by the absence of sexual development by the age of 15 years in boys and by the age of 14 years in girls [3]. Delayed puberty warrants endocrinological investigation. Treatment depends on the cause.
Delayed puberty is usually due to constitutional delay, ie puberty is late but otherwise occurs normally. The onset of puberty can be delayed by factors such as malnutrition or excessive exercise, by interfering with the hypothalamic control of the initiation of puberty.
