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3002 > 78 Puberty > Flashcards

78 Puberty Flashcards

1
Q

What is puberty?

A

• Developmental stage during which adolescents reach sexual maturity and become capable of reproduction
• Involves physiological processes of adrenarche and gonadarche
• Results in:
- growth of stature
-change in body composition
-development of secondary sexual characteristics
-achievement of fertility

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2
Q

Definition of adrenarche?

A
  • Increase in production of androgens by adrenal cortex

* Androgens = steroid hormones e.g. testosterone

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3
Q

Definition of gonadarche?

A
  • Activation of the gonads by gonadotrophin

* Gonadaotrophins = FSH and LH from pituitary

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4
Q

Difference between primary and secondary sexual characteristics?

A
  1. Primary sexual characteristics
    • Reproductive organs, present ar birth
  2. Secondary sexual characteristics
    • Develop during puberty, not directly required for reproduction
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5
Q

Definition of thelarche?

A

Onset of breast development

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6
Q

Definition of pubarche?

A

First appearance of pubic hair

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7
Q

Definition of menarche?

A

Onset of menstruation

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8
Q

What area of adrenal gland releases androgens?

A

Zona retiulcaris of adrenal cortex

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9
Q

What occurs in Adrenarche (Hypothalamic-Pituitary-Adrenal axis)?

A

• Primary stimulus = enhanced adrenal sensitivity to ACTH
• Maturational increase in adrenal androgen (DHEA-S) production
• Around age 6 in boys and girls
• Occurs in conjunction with gonadal maturation
• Increased androgen levels responsible for:
- Development of pubic and axillary hair (pubarche)
- Development of pilosebaceous unit in the skin (acne)
- Increases cortical bone density

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10
Q

Events of puberty in females?

A
  1. Breast development:
    • 1st sign
    • Between 8.5 - 12.5 years

2.Pubic hair growth and rapid height spurt:
• Occurs almost immediately after breast development

  1. Menarche:
    • Average age 13
    • On average 2.5 years after start of puberty
    • Signals the end of growth (only ~5cm height gain remaining)
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11
Q

List the female secondary sexual characteristics?

A
  • Breast budding (Thelarche)
  • Onset of pubic hair (Pubarche)
  • Maximal growth velocity
  • Menarche
  • Development of axillary hair
  • Attainment of the adult breast type
  • Adult pubic hair pattern
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12
Q

In total, thelarche, growth spurt, pubarche and menarche requires how many years?

A

4.5 years (range 1-6)

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13
Q

What is the tipping point to the beginning of menarche?

A
  • As the ovaries mature, becomes more sensitive to gonadotrophin and release more steroid hormones
  • Early cycles may be anovulatory
  • Up to 18 months for regular ovulatory cycles to develop
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14
Q

Tanner Stages in females?

A

Scale (I-V) of physical development in children, adolescents and adults

• Breast and pubic hair

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15
Q

What is the HPA axis?

A

Hypothalamic- Pituitary- Adrenal axis

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16
Q

What is the HPO axis?

A

Hypothalamus pituitary ovarian axis

17
Q

Signs of male puberty?

A
  1. Testicular enlargement to greater than 4mls volume:
    • 1st sign
    • 10-15 years (mean 11)
  2. Pubic hair growth and penile growth:
    • Normally 2 year interval between the onset of pubic hair and axillary and facial hair
  3. Spermarche -appearance of sperm in seminal fluid
    • Mean age 13.4
  4. Growth spurt:
    • When testicular volume is 12-15mls, after a delay of ~ 18 months
    • Growth spurt in males later and of greater magnitude accounting for greater average final height in males
18
Q

Tanner stages in males?

A

Scale (I-V) of physical development in children, adolescents and adults

• Testes, scrotum, penis, pubic hair

19
Q

What is a Prader Orchidometer?

A

Medical instrument used to measure the volume of the testicles

20
Q

What is the HPG axis?

A

Hypothalamic Pituitary Gonadal (HPG) axis

  • FSH/ LH promotes testes to produce sex steroids - testosterone
  • FSH promotes testicular enlargement
  • Testosterone promotes penile enlargement
  • Testosterone criitcal for spermatogenesis
21
Q

Male androgen-dependent secondary sexual characteristics?

A

Virtually all dependent on testosterone and its metabolite DHT

  • Facial, underarm, pubic hair
  • Deepening of voice (due to growth of larynx)
  • Thick secretion of skin oil glands (can cause acne)
  • Masculine pattern of fat distribution
  • Bone growth via growth hormone secretion - then termination via closure of epiphyseal plates
  • Stimulation fo muscle protein synthesis
  • Erythropoietin stimulation giving higher haematocrit in males
22
Q

How is puberty initiated (hypothalamic-Pituitary-Gonadal axis)?

A

• Gonadotrophin (LH/ FSH) release:
- Suppressed by continuous infusion of GnRH
- Pulsatile administration will lead to gonadal stimulation, maturation and production of steroid hormones
• ‘Juvenile pause’ characteristic of all higher primates
• Pulses of GnRH are detectable in the childhood years but mostly during sleep and of low frequency and amplitude therefore do not stimulate gonadotropin release
• Unknown signal - GnRH pulse generator
• Nocturnal secretion of GnRH pulses become more pronounced leading to gonadotrophin release

23
Q

4 phases of human growth?

A
  1. Fetal:
    • Uterine environment
    • Fastest
    • 30% of eventual height determined
  2. Infantile:
    • Nutrition, general health, happiness and thyroid function • Birth - 18 months - rapid but decreasing growth rate
    • 15%
  3. Childhood:
    • Dependent on thyroid hormones, growth hormone, general health and happiness, genetics
    • Slow steady prolonged
  4. Pubertal:
    • Sex hormones esp. testosterone and oestrogen, growth hormones and insulin-like growth factor
24
Q

What is the peak velocity of girls and boys?

A
  • Girls mean age 11.5 (9cm/y)
  • Boys mean age 13.5 (10c/y)

• PHV occurs relatively earlier in girls (tanner stage 2-3) compared to boys (tanner stage 3-4)

25
Q

Why are boys taller?

A

Late onset of growth spurt in boys (~ 2 years) accounts for overall greater final height as they achieve more growth before peak velocity

26
Q

Why does puberty limit heights?

A

Puberty limits adult height as gonadal steroids lead to epiphyseal closure of long bones

27
Q

Difference in male and female body composition?

A

In adults:

  1. Males
    • Gain greater amounts of fat-free mass and skeletal mass
    • Changes in body composition from ~9y
  2. Females
    • Acquire significantly more fat mass
    • Changes in body composition from ~6y
28
Q

Factors contributing to earlier puberty?

A
  1. Genetic:
    • Fhx of early puberty
    • TIming correlates with mother and sisters
2. Social factors:
• Lower social class and obesity = earlier menarche
  1. Geographic factors:
    • Close to equator, lower altitudes, urban setting
  2. Environmental exposure:
    • Endocrine disrupting chemical s
    • Industry uses e.g. plastics, agriculture, fuels
  3. Race:
    • Onset earlier in Afro-Carribean and African-American children compared to white children
29
Q

Describe link between nutrition and pubertal development?

A

• Some evidence that obesity accelerates onset in girls
• Progression affects by prepubertal body composition (fat mass and BMI) in boys and girls
• Increase in body fat may play a critical role int he turning on of the adrenal androgen secretion and adrenarche:
- Leptin may be link between adipose tissue, energy homeostasis centres in hypothalamus and the reproductive system

30
Q

What are the stages of ovarian failure in menopause?

A
  • Cycles become regular as women reach climacteric age 40 (10 years of change that leads to menopause)
  • Between 45-55 years (average 51.5)
  • Follicle supply diminishes
  • Follicle cells gradually become insensitive to FSH and LH
  • Ovarian steroid levels fall
  • No -ve feedback to the pituitary therefore dramatic increase in levels of FSH (10-20x: excreted in urine) and LH (3x)
  • Low levels of sex steroids are produced by the adrenals
31
Q

Menopause symptoms?

A

• Vascular instability - night sweats and hot flushes
• Atrophy of all oestrogen dependent tissues:
- Breast, uterus, vagina, bladder, urethra (atrophic vaginitis)
- Skin collage loss
- Bone catabolism with loss of Ca2+ leads to osteoporosis
- LDL rises (increases risk of coronary thrombosis)
• Rise in adrenal androgens may lead to hirsutism
• Loss of libido
• Depression, anxiety, mental confusion

32
Q

Treatment of menopause?

A

HRT replaces steroids, maintains oestrogen dependent tissues and delays osteoporosis

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