Puberty and Lactation

Question 1

Puberty

Answer 1

is a developmental stage (physical changes) during which adolescents reach sexual maturity and become capable of reproduction

Question 2

puberty Involves physiological processes of

Answer 2

– Gonadarche = physical and functional maturation of the gonads by gonadotrophins • Gonadotrophins are FSH & LH from pituitary
– Adrenarche = increase in production of androgens by adrenal cortex • Androgens are steroid hormones e.g. dehydroepiandrosterone (DHEA)

Question 3

what does puberty result in

Answer 3

– Growth in stature
– Change in body composition
– Development of secondary sexual characteristics (pubarche)
– Achievement of fertility

Question 4

primary reproductive characteristics

Answer 4

– Reproductive organs, present at birth

Question 5

Secondary sexual characteristics

Answer 5

– Develop during puberty, not directly required for reproduction

Question 6

Thelarche

Answer 6

onset of breast development

Question 7

Pubarche

Answer 7

first appearance of pubic hair

Question 8

Menarche

Answer 8

onset of menstruation

Question 9

Hypothalamic-Pituitary-Adrenal Axis (Adrenarche)

Answer 9

• 6-8 years of age
• ACTH produced by pituitary
• Stimulates adrenal glands to secrete androgens – predominantly DHEAS (dehydroepiandrosterone sulphate)

Question 10

• Increased androgen levels responsible for

Answer 10

– Development of pubic and axillary hair (pubarche)
– Development of pilosebaceous unit in the skin - acne
– Increases cortical bone density

Question 11

Breast development

Answer 11

– first sign

– usually between 8.5 and 12.5 years

Question 12

Pubic hair growth and rapid height spurt

Answer 12

– occur almost immediately after breast development

Question 13

• Menarche

Answer 13

– average age 13
– on average 2.5 years after the start of puberty
– signals the end of growth (only around 5cm height gain remaining)

Question 14

Secondary Sexual Characteristics development in women

Answer 14

• Virtually all dependent on oestrogen and progesterone
• Hormone-dependent secondary sexual characteristics
– Facial, underarm, pubic hair
– Thick secretion of skin oil glands (can cause acne)
– Female pattern of fat distribution (breasts, hips, buttocks, thighs, upper arms)
– Hips and pelvis widen
– Uterus and cervix enlarge, secretory function increases
– Bone growth via growth hormone secretion then termination via closure of epiphyseal plates

Question 15

• Testicular enlargement to greater than 4mls volume

Answer 15

– first sign, 10-15 years (mean 11)

Question 16

Pubic hair growth and penile growth

Answer 16

– Normally 2 year interval between onset of pubic hair and axillary and facial hair

Question 17

Spermarche – appearance of sperm in seminal fluid

Answer 17

– mean age 13.4 (stage 3-4 of testicular growth)

Question 18

Growth spurt

Answer 18

– when testicular volume is 12-15mls, after a delay of around 18 months
– Growth spurt in males later and of greater magnitude accounting for greater average final height in males

Question 19

Secondary Sexual Characteristics development in men

Answer 19

• Virtually all dependent on testosterone and its metabolite dihydrotestosterone (DHT)
• Androgen-dependent secondary sexual characteristics
– 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 of muscle protein synthesis
– Erythropoietin stimulation giving higher haematocrit in males

Question 20

Initiation of Puberty

Answer 20

• Gonadotropin (LH/FSH) release
– Suppressed by continuous infusion of GnRH
– Pulsatile administration will lead to gonadal stimulation, maturation and production of steroid hormones

Question 21

initiation of puberty method

Answer 21

• 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 gonadotropin release

Question 22

Factors Contributing to Earlier puberty

Answer 22

• Genetics
– Timing correlates with mother and sisters
• Social factors
– Lower social class & obesity tends to lead to earlier
menarche
• Geographic factors
– closer to equator, lower altitudes, urban setting • Environmental exposures
– endocrine disrupting chemicals – industry uses e.g. plastics, agriculture, fuels
• Race
– onset earlier in Afro-Carribean and African-American
children compared to white children
• Exact mechanism that signals start of puberty is unknown but body weight and other metabolic factors may play a key role

Question 23

WHO/UN advises women to breast feed exclusively for

Answer 23

6 months for
optimal lifetime benefits
• Reduced incidence of GI, respiratory and middle ear infection
• Decreased risk of childhood diabetes, asthma and eczema
• Reduced risk of lactose intolerance
• Improved intellectual and motor development
• Decreased risk of obesity in later life
• Possible reduced autoimmune diseases
• 27% reduced risk of sudden infant death syndrome

Question 24

wha benefits does lactation have for the mother

Answer 24

• Promotes recovery from childbirth
• Promotes return to ‘normal’ body weight
• Promotes a period of infertility
• Reduces risk of premenopausal breast cancer
• Reduces risk of ovarian cancer
• Possibly improves bone mineralisation

Question 25

Anatomy of the Breast

Answer 25

• Nipple is surrounded by pigmented skin (areola)
• Modified sebaceous glands (alveoli) empty via lactiferous ducts that are dilated to form lactiferous sinuses which open on the surface of the nipple
• Adipose tissue is dominant in the non- lactating breast
• Glandular tissue only develops fully during pregnancy

Question 26

• Secretory alveoli

Answer 26

– milk producing cells

– stimulated by prolactin

Question 27

• Each alveolus

Answer 27

– surrounded by contractile myo-epithelial
cells
– stimulated by oxytocin

Question 28

Prolactin

Answer 28

• Initiated by precipitous drop in oestrogen and progesterone after delivery
• Prolactin surges each time mother nurses baby due to nerve impulses from nipples
to hypothalamus
• Without nursing stimulation, no prolactin surge and loss of milk production
• When not nursing, hypothalamus produces prolactin inhibitory hormone
• Lactation inhibits FSH and LH and thus lactation interferes with reproductive function

Question 29

How is Lactation Inhibited During Pregnancy?

Answer 29

• Prolactin levels increase during pregnancy - stimulates growth and development of the mammary tissue
• Prolactin controls / promotes milk production
• Prolactin is secreted during pregnancy (from anterior pituitary), but its action is inhibited by high levels of progesterone and oestrogens and hPL (human placental lactogen)
• These steroid levels fall after parturition and milk production begins