• Clinical science

Puberty

Abstract

Puberty refers to the phase of development between childhood and adulthood in which complete functional maturation of the reproductive glands and external genitalia occurs. The other processes that characterize this transitional phase are the development of secondary sex characteristics, growth spurts, and psychosocial changes. The stages of development during puberty are classified according to the Tanner stages. Although there is considerable variation between individuals, on average puberty begins at the age of 11 in girls and 13 in boys. Puberty that begins abnormally early is referred to as precocious puberty and can be due to a peripheral cause (peripheral precocious puberty) or a central cause involving the hypothalamo-hypophyseal axis (central precocious puberty, or CPP). At the other end of the disease spectrum, puberty may be delayed or absent. This delay can be constitutional, secondary to underlying conditions, or due to hypogonadism.

Normal puberty

  • Definition: phase of development between childhood and complete, functional maturation of the reproductive glands and external genitalia (adulthood)
  • Phases of pubertal changes
  • Physiology: unknown initial trigger → ↑ activators and/or ↓ inhibitors of GnRH secretion → GnRH pulsing FSH and LH levels
  • Influential factors
    • General health (nutritional state, body weight)
    • Genetics
    • Social environment (e.g., family stress)
  • Girls
    • Normal age of onset: 8–13 years
    • Normal order of changes: adrenarchegonadarchethelarche (age of onset 8–11 years) → growth spurt (age of onset 11.5–16.5 years) → pubarche (mean age of onset 12 years)→ menarche (age of onset 10–16 years ; mean age: 13 years)
  • Boys
    • Normal age of onset: 9–14 years
    • Normal order of changes: adrenarchegonadarche (age of onset 9–14 years) pubarche (mean age of onset 13.5 years)→ growth spurt (mean age of onset 13.5 years) → androgenic hair growth

The first visible sign of puberty in males is testicular enlargement, while in females it is breast development.

References:[1][2][3][4][5]

Physical changes during puberty

Tanner stages

Development of pubic hair (boys and girls)
Ph1 Usually no pubic hair, vellus hair possible
Ph2 Sparse, lightly pigmented hair (straight or curled) on the labia/base of the penis
Ph3 Dark, coarse, curly hair spreading over the pubic symphysis
Ph4 Adult pubic hair that does not extend to the inner thighs
Ph5 Adult pubic hair that extends to the inner thighs with horizontal upper border
Ph6 Further growth of pubic hair along linea alba in the direction of the umbilicus (in 80% of men and 10% of women)
Breast development (girls)
B1 Prepubertal appearance and size; occasional elevation of the nipple
B2 Enlarged mammary glands form a breast bud; slight increase in areolar diameter, nipple protrusion
B3 Further enlargement of mammary glands; breast bud extends beyond the areolar diameter
B4 Nipple and areola form a secondary mound which projects above the breast tissue
B5 Adult breast; areola with projection of papilla only
Genital development (boys)
G1 Prepubertal appearance and size of the testes, scrotum, and penis
G2 Testicular volume of 4 mL; larger scrotum; no penile enlargement; scrotal skin changes darkens in color and texture
G3 Continued enlargement of the testes and scrotum; longer penis
G4 Testicular volume of 12 mL; scrotum growth; longer and wider penis
G5 Testes, scrotum, and penis attain adult appearance and proportions

Other morphological changes during puberty

  • Breast changes (boys):
    • Occur approximately within 18 months of pubertal onset in males; usually during Tanner stage 3
    • Lasts for ∼ 6–18 months
    • Gynecomastia is diagnosed in a pubertal male when the palpable subareolar gland and ductal tissue is ≥ 2 cm.
    • See pubertal gynecomastia.
  • Growth spurts
    • Vary between the sexes (occurs two years earlier in girls); lasts for ∼ 2 years
    • Includes ↑ growth in trunk and limbs
    • Assessed using growth velocity charts
  • Bone growth
    • Accelerated during puberty
    • Order of growth: ↑ length↑ width↑ mineral content ↑ density
  • Body weight and composition
    • Boys: ↓ body fat (early puberty) → ↑ lean body mass (later puberty)
    • Girls: gradual ↑ body fat
    • Affected by nutritional status
  • Skin changes: : pubertal hormonal fluctuation → sebum secretion and excessive sweating → acne vulgaris, hyperhidrosis, and hair problems (e.g., seborrheic dermatitis)
  • Myopia: due to axial growth of the eye
  • Other physical changes associated with menarche:

References:[3][6]

Stages of adolescence

Adolescence is the period of physical and psychological development from the onset of puberty to adulthood (age of majority). Adolescence is associated with an increased risk of mortality and morbidity due to an increase in risk-taking behavior.

Stage of adolescence

Onset Features
Early 10–14 years
  • Self-esteem and body issues
Middle 15–16 years
  • Development of an independent identity
  • Mood swings
  • Narcissistic within relationships
Late ≥ 17 years
  • Less egoistic
  • Develops closer relationships with individuals
  • Idealistic thoughts
  • Awareness of the future

Precocious puberty

Central precocious puberty

Peripheral precocious puberty

Central precocious puberty has a central cause (e.g., hypothalamic lesions) and high GnRH levels; precocious pseudopuberty has a peripheral cause (e.g., germ cell tumors), without elevated GnRH levels!

Benign pubertal variants

Obesity-related precocious sexual development

References:[1][2][7][8][9][10][11]

Delayed onset of puberty

  • Definition: absent or incomplete development of secondary sex characteristics by the age of 14 in boys or 13 in girls
  • Etiology
    1. Constitutional growth delay (most common cause of delayed puberty)
      • Definition: a temporary delay in growth and onset of puberty that is not caused by any pathological process
      • Etiology: may be inherited as an autosomal dominant, recessive, or X-linked trait
      • Diagnosis: X-ray showing a bone age that is less than the individual's chronological age
      • Treatment: No treatment is needed, as catch-up growth eventually occurs and the individual reaches a normal adult height.
    2. Malnutrition and other chronic diseases (such as inflammatory bowel disease, hypothyroidism, or psychosocial deprivation)
    3. Hypogonadism
  • Diagnosis
    • Monitoring over time
    • History: delayed (not interrupted!) growth, nutritional habits, medication, positive family history of delayed onset of puberty
    • X-ray of the hand
      • Allows association between skeletal maturation and chronological age
      • Shows delayed bone age
    • Basal LH and FSH
    • In the case of primary amenorrhea → also measure TSH and prolactin
  • Therapy
    • Treatment of the underlying disease
    • Watchful waiting: careful serial growth measurements at frequent intervals ∼ every 6 months
    • When pubertal delay is severe: gonadal steroids

References:[1][12][13][14]