1. Puberty and associated changes

2. Puberty
Sexual maturity
Physical
Behavioral
Physiological

3. Signs of puberty Females Males Ovulation Menstruation Somewhat unclear
First ejaculation with viable sperms
Minimum number required to achieve successful conception

4. Puberty and fertility First menstruation/ejaculation
Not the sign of fertility
Signs of gonadal development
Changes in gonadotropin secretion
Changes in gonadotropin responsiveness
Changes in steroid hormone production
Changes in gametogenesis

5. Physical changes Rapid growth Phases Earlier in females Minimum growth
Peak growth velocity (PGV)
Epiphseal fusion
End of growth
Earlier in females

6. Involvement of skeletal and muscular system
Regional differences in rate of growth
Dimorphism
Changes in body composition
Amount of fats within the body
Distribution of fats
Changes take place before puberty
Earliest difference in males and females during puberty

7. Endocrine regulation
Synergism between growth hormone (GH) and steroid hormones (estradiol or testosterone)
Increased secretion of GH
Increased responsiveness to GH
GH receptors

8. Activation of gonads Development of secondary sex characteristics
Breasts
External genitalia
Hair distribution
Pubic hair
Facial hair
Axillary hair
Larynx (vocal cord) and laryngeal muscles
Deepening of voice

9. Role of steroid hormones
Estradiol
Breast development
Development of mammary alveolar tissue
Female external genitalia
Progesterone
Development of mammary ducts

10. Role of steroid hormones
Androgens
Male genitalia
Hair growth and distribution
Male and female
Larynx and laryngeal muscles
Events associated with puberty
Sequential
Critical for clinical examination

12. Endocrine control of puberty
Secretion of gonadotropin
Very low during childhood
Increase in FSH and LH secretion
Stimulation of follicular development
Stimulation of steroidogenesis
Circadian pattern of gonadotropin secretion

14. Secretion of prolactin
Increased in females
Response to increased estradiol level
Steroidogenesis
Increased testosterone production
Follows LH pattern
Increase by 12 folds (0.2 ng/ml to 2.4 ng/ml)

15. Production of estradiol
Increase during puberty in females
Similar level with adult
Production of adrenal steroids
Androgens (DHEA)
Specific
No increase in glucocorticoids or mineralocorticoids
Adrenarche
Starts around 8 years of age and continues until years old

17. Production of adrenal steroids
Androgens (DHEA)
Specific
No increase in glucocorticoids or mineralocorticoids
Adrenarche
Starts around 8 years of age and continues until years old
Very high concentrations compared to gonadal steroids
Promotion of hair growth and distribution in both sexes

18. Changes in secretion of gonadotropins
Two theories
Gonadostat theory
Progressive maturation of feedback action of steroids
Changes in responsiveness of the anterior pituitary gland to GnRH
Central maturational role to the CNS
Hypothalamus

19. Gonadostat theory Prepubertal period Ovaries
Some antral/tertiary follicles
Estradiol production (very low)
Negative feedback of estradiol on gonadotropin secretion
Greater sensitivity to estradiol
Low threshold

20. Pubertal period Changes in sensitivity to estradiol
Increased threshold
Decreased sensitivity
Increased responsiveness of pituitary gland to GnRH stimulation
All of these are secondary response
Leads to increased production of steroid hormones
Increased secretion of gonadotropins

21. Delayed appearance of positive feedback
Reproductive cycle during early puberty
May not accompanied by ovulation
Capacity to evoke LH surge
Requires repeated exposure to high concentrations of estradiol
Ovulatory LH surge
Later portion of puberty
Estradiol concentrations may be too low

22. E (+) GnRH GnRH FSH FSH Prepubertal period Puberty E (-) Hypothalamus
Pituitary gland
Pituitary gland

23. Hypothalamus maturation model
Pubertal activation of hypothalamus
Increased output of GnRH
The CNS rather than gonadal axis
Changes in GnRH pulsatility
No alteration in pituitary or ovarian response
Independent of steroid exposure

26. Effects of environment
Decreasing age to the first menstruation and male puberty
Western countries
Advanced health care
Economics
Wellness
Majority of women will experience menopause
Increased life expectancy
Other health issues

27. Role of light exposure Critical for animals with breeding seasons
Requires exposure to increasing length of daylight (long-day breeders)
Horses
Requires exposure to decreasing length of daylight (short-day breeders)
Sheep
Wild species

28. Role of nutrition Attaining critical body weight
Critical for initiation of the reproductive cycle
Domestic species (i.e. cattle)
Body weight rather than actual age determines when animals reach puberty
Humans
Same as the domestic species
Activation of hypothalamus-pituitary-gonad axis
Growth spurt

29. Body size (weight and height)
May be critical
Pregnancy
Women with eating disorder (anorexia)
Maintenance of critical body weight (47 kg)
Irregular/cessation of menstrual cycle

30. Actual body weight vs. fatness of the body
Lean people (i.e. athletes)
Later initiation of menstrual cycle compared to moderately obese individuals
Low body fat content
Irregular menstrual cycle
Cessation of menstrual cycle

31. Metabolic signals Leptin Hormone produced by fat cells Satiety factor
Decreases appetite
Energy levels within the body
Unclear linkage