Physiological Changes D uring P uberty & Menopause

1. بسم الله الرحمن الرحيم Physiological Changes During Puberty & Menopause Dr.Mohammed Sharique Ahmed Quadri Assistant professor physiology Al Maarefa College

2. Objectives • Define puberty • List the factors that affect time of onset of puberty in boys and girls • Describe the hormonal changes that take place during puberty in boys and girls • Outline the functions of pituitary, gonadal and adrenal hormones during puberty • Define menopause • Distinguish the hormonal changes that takes place during menopause

3. Definition of Puberty: Pubertyis the stage of physical maturation in which an individual becomes physiologically capable of sexual reproduction.

4. Onset of Puberty • Wide variation in the onset and duration of puberty • Males vs. females • Ethnic and racial groups • Individual difference(genetic factor) • On average It usually begins between the ages of 10-14 years,( two years earlier in females than males )

5. Endocrine Regulation of Reproduction • Hypothalamus releases LHRH (GnRH) into hypothalamo-hypophyseal portal vessels. • Anterior pituitary secretes: • LH (luteinizing hormone). • FSH (follicle-stimulating hormone). • GnRH Secreted in pulsatile fashion to prevent desensitization and down regulation of receptors.

6. Endocrine Interactions • Anterior pituitary secretes LH and FSH. • Secretion of LH and FSH stimulated by LHRH (GNRH). • Primary effects of LH and FSH on gonads: • Stimulation of spermatogenesis and oogenesis. • Stimulation of gonadal hormone secretion. • Maintenance of gonadal structure.

7. Endocrine Regulation • Negative feedback: • Inhibits GnRH from hypothalamus. • Inhibits anterior pituitary response to GnRH. • Inhibin secretion inhibits anterior pituitary release of FSH. • Female: • Estrogen and progesterone. • Male: • Testosterone.

8. Onset of Puberty • FSH and LH secretion is high in newborn, but falls to low levels in few weeks. • At puberty secretion of GnRH,FSH,& LH increases and become pulsatile. • Pulsatile pattern of hypothalamo pituitary axis is required for normal reproductive functions.

9. How does puberty begin ? • During childhood , the hypothalamus is extremely sensitive to the negative feedback exerted by the small quantities of estradiol & testosterone produced by the child's ovaries or testes .

10. As puberty approaches , the sensitivity of the hypothalamus is decreased and subsequently , it increase the pulsatile GnRH secretion initially at night . • The anterior pituitary responds by progressive secretion of FSH and LH associated with increased secretion of growth hormone .

11. In female • The ovaries respondto the increase Gonadotrophin secretion by follicular development & estrogen secretion . • Estrogen causes development of the genital organs and the appearance of the secondary sexual characters . • With increased estrogen secretion , menarche occurs.

12. Puberty in Girls • The sequence of events in girls are as follows • THELARCHE: The development of breast • PUBARCHE: The development of axillary and pubic hairs • MENARCHE: The first menstrual period

13. Pubertal Changes in Females • Folliculogenesis proceeds • Ovulation for first time • Increase of Estradiol and progesterone • Secondary sexual characteristics: • Broadening of hips • Subcutaneous fat( buttocks, breast, thighs) • Growth of external genitalia • Pubic hair • Increased sebaceous gland secretions (adrenal androgens)

14. In Males • The testis respond to the increase Gonadotrophin secretion by increase in testicular size and increase testosterone secretion . • Testosterone causes development of the genital organs and the appearance of the secondary sexual characters .

15. Pubertal Changes in Males • Spermatogenesis initiates • Increased androgen secretion • Growth of accessory sex structures • Prostate • External genitalia • Male secondary sex characteristics • Facial and body hair • Growth of larynx( deepening of voice)

16. CHRONOLOGICAL ASPECT(changes in boys and girls at puberty) GIRLS • Acceleration of growth rate • Development of breasts and pubic hair • Axillary hair • Menarche BOYS • Increase of testicular volume • Increase of penile length • Pubic hair • Increased growth rate • Axillary hair • Deepening of the voice

17. What causes initiation of puberty in humans ? • The mechnismunderlyig the pulsatile GnRH secretion remain unclear. The theories proposed are • Melatonin secretion by pineal gland • Leptin secretion by adipose tissue

18. Factors responsible for initiating pubertyMelatonin secretion • Melatonin is secreted by pineal gland . • Secretion decreases by exposure to light and increses during exposure to dark • It is suggested that , there is observed decrease in rate of melatonin secretion at puberty, particularly at night , when peak in GnRH secretion first occur- is the trigger for onset of puberty.

19. Factors responsible for initiating pubertyLeptin secretion • A satiety producing hormone • Secreted by adipose tissue • May play role in hypothalamic maturation at puberty ( delayed onset of puberty in lean or caloric deprived girls )

20. Menopause • Cessation of woman’s menstrual cycle (Absence of menstrual cycle for at least 12 consecutive months) • Usually occurs between ages of 45 and 55

21. What Causes Menopause • Midlife hypothalamic change may trigger onset of menopause • limited supply of ovarian follicles present at birth. Once this reservoir is depleted ovarian cycle and menstrual cycle ceases • Follicular reserve provides an exhaustible source of oocytes that is established around the time of birth

22. Menopause • Preceded by period of progressive ovarian failure characterized by • Increasingly irregular cycles • Dwindling estrogen levels • Loss of estrogen primarily affects skeleton and cardiovascular system • Period of transition from sexual maturity to cessation of reproductive capability is called the climacteric or perimenopause.

23. Menopause (Reproductive Decline) • Cessation of menstrual cycle • Loss of ovarian function • Infertility • Drop in ovarian steroids (estrogen and progesterone) • Rise in gonadotropin hormones • Decrease in ovarian inhibin production

24. Symptoms of Menopause • Hot flashes/flushes • Mood swings • Vaginal dryness • Depression • Incontinence • Change in sex drive Risk of cardiovascular diseases and osteoporosis increases

25. Hormone Replacement Therapy • Estrogen is taken on a daily basis while progesterone is taken less regularly • Helps alleviate symptoms such as hot flashes, vaginal dryness and mood swings • Slows the progress of osteoporosis; decreased rate of fractures

26. Andropause • Male reproductive aging • Very gradual compared to menopause • Gradual decrease in sperm production and in testosterone production may occur after 45 to 50 years • Results from degenerative changes in small testicular blood vessels

27. References • Human physiology by Lauralee Sherwood, seventh edition • Text book physiology by Guyton &Hall,11th edition • Text book of physiology by Linda .s contanzo,third edition