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Physiological Changes During Puberty & Menopause

Dr.Mohammed Sharique Ahmed QuadriAssistant professor physiology

Al Maarefa College

بسم الله الرحمن الرحيم

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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

Definition of Puberty:

Puberty is the stage of physical maturation in which an individual becomes physiologically capable of sexual reproduction.

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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 )

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.

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.

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.

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.

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 .

• 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 .

In female

• The ovaries respond to 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.

Puberty in Girls

• The sequence of events in girls are as follows

I. THELARCHE: The development of breast II. PUBARCHE: The development of axillary and

pubic hairs

III. MENARCHE: The first menstrual period

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)

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 .

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)

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

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• 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

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.

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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 )

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

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

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.

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

Symptoms of Menopause

• Hot flashes/flushes• Mood swings• Vaginal dryness• Depression• Incontinence• Change in sex drive

Risk of cardiovascular diseases and osteoporosis increases

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

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

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