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Physiology & Science: Reproduction > Puberty and Its Disorders > Flashcards

Puberty and Its Disorders Flashcards

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1
Q

What is puberty and what happens?

A
  • Transition from non-reproductive to reproductive state
  • Secondary characteristics develop (primary present at birth)
  • Adolescent growth spurt
  • Profound physiological + psychological changes
  • Gonads produce mature gametes (spermatozoa + oocytes)
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2
Q

Name the two endocrine events of puberty

A
  • Adrenarche
  • Gonadarche

Both occur independently of each other

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3
Q

What is adrenarche?

A
  • Change in adrenal androgen secretion (from zona reticularis), the two androgens are DHEA and DHEAS
  • Occurs ages 6-8, peaks at 20-25
  • Growth of pubic + axillary hair
  • Growth in height
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4
Q

What is adrenopause?

A

The end of adrenarche - the decline in DHEA/DHEAS

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5
Q

What is pubarche?

A
  • Appearance of pubic/axillary hair
  • Induced by adrenal androgen secretion
  • Associated with acne due to inc sebum prod, infection + abnormal keritinization
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6
Q

What is gonadarche?

A
  • Several years after adrenarche (~11)
  • Reactivation of hypothalamic GnRH
  • Activation of gonadal steroid production -> prod of viable gametes + ability to reproduce
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7
Q

Where is GnRH released from and in what manner?

A
  • Released from GnRH neurons (specialist hypothalamic centres)
  • Pulsatile secretion essential for GnRH function
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8
Q

What is meant by ‘reactivation of GnRH’ during gonadarche?

A

The HPG axis is first activated at the 16th gestational week, pulsatile GnRH secretion in foetus until 1-2 years postnatally when it ceases.

Then re-activated at ~11 years - during gonadarche.

The GnRH neurones ‘restrained’ during postnatal period -> 10 years or more. At puberty a gradual rise in pulsatile release of GnRH.

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9
Q

How do we know GnRH rises during puberty?

A
  • Early-mid puberty there is a nocturnal rise of GnRH secretion
  • But we measure LH levels as GnRH cannot be easily measured (as it’s in hypophyseal circulation)
  • LH secretion increases during pubertal development
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10
Q

What stimulates the onset of puberty?

A

Clear that it is a maturational event within the CNS

  • Inherent (genetic) maturation of 1000-3000 GnRH synthesising neurones
  • Environmental/genetic factors
  • Body fat/nutrition
  • Leptin
  • Other gut hormones
  • Kisspeptin
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11
Q

Frisch et al

Describe the link between fat metabolism and reproduction

A

Certain % fat:body weight necessary for menarche (17%) and required (22%) to maintain reproductive ability

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12
Q

What impact does anorexia nervosa (or intensive physical training) have on puberty?

A
  • Reduced response to GnRH
  • Decrease gonadotrophin levels
  • Amenorrhea
  • Restored when nourished/exercise stopped
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13
Q

What is the role of kisspeptin?

A

Gateway for puberty, kisspeptin receptors (GPR54) are expressd on GnRH neurones.

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14
Q

What can mutations of GPR54 or the gene coding for kisspeptin lead to?

A
  • abnormal development of GnRH neurones -> hypogonadotrophic hypogonadism
  • failure to enter puberty
  • activating mutations of kisspeptin receptor -> precocious puberty
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15
Q

What is meant by ‘consonance’?

A

Consonance describes the smooth ordered progression of changes that occur during puberty.

  • Age of onset, pace & duration of changes (these can be different between individuals)
  • But the stages and order of the stages remain the same
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16
Q

What is the average age of menarche onset (UK)?

A

First menstrual period - ~ 12.5 (on the decline)

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17
Q

Briefly describe the Tanner stages of puberty

A
  • 1 - prepubertal
  • 2 - early puberty, breast-budding + inc in testicular vol (>4ml)
  • 3/4 - mid-late stage of puberty
  • 4 - adult phenotype, completion of puberty
18
Q

What stimulates breast development?

A

Oestrogen

19
Q

What stimulates penile and scrotal development?

A

Testosterone

20
Q

What stimulates testicular enlargement as well as follicular development?

A

FSH

21
Q

What are the physical changes in girls during puberty?

A
  • Breasts enlarge (thelarche)
  • Pubic/axillary hair
  • Uterus enlarges
  • Uterine tubes, vagina, cervical changes
  • Height + body shape
  • HPG axis
  • Menarche (not = fertility)
  • Fertility (after about a year)
22
Q

What are the physical changes in boys during puberty?

A
  • External genitalia: test vol >4ml, growth of penis, scrotum
  • Vas deferens (lumen increases)
  • Seminal vesicles + prostate
  • Facial/body hair
  • Pubic/axillary hair
  • Larynx (enlarged via androgens), adams apple, deeper voice
  • Height + body shape
  • Onset of fertility from beginning of puberty
23
Q

Describe growth spurt in boys and girls

A
  • Girls - PHV (peak height velocity) = 9cm/y @ 12 years (earlier)
  • Boys - PHV = 10.3cm/y @ 14 years
  • Complex interaction between GH and oestrogen, oestrogen has a biphasic effect on epihyseal growth:
  • Low levels -> linear growth + bone maturation
  • High levels -> eipihyseal fusion
24
Q

What is the Prader Orchidometer?

A
  • Series of numbers on beads representing diff volumes in cms
  • Used to measure testicular size in boys at diff ages
  • Orchidometer in one hand, testicle in other hand and then measured against each other
25
Q

What is the effect of androgens on the differentiation of pilosebaceous units (PSUs)?

A
  • stimulate sebum secretion + w/ infection -> acne
  • induce differentiation of vellus(*) PSUs -> terminal PSUs (mustache+beards)
  • induce differentiation of vellus PSUs -> apo-PSUs (pubic+axillary hair)

*vellus PSUs are the undifferentiated ones, aka childhood hairs

26
Q

What are the psychological changes associated with puberty?

A
  • Increasing need for independence
  • Increasing sexual awareness/interest
  • Development of sexual personality

Later maturation = better adjustment

27
Q

What is precocious puberty?

A

Development of any secondary sexual characteristic before age of 8 in girls and 9-10 in boys.

Precious puberty is when pubertal changes are early but in consonance.

28
Q

Describe gonadotrophin-dependent (or central) precocious puberty

A
  • Consonance
  • Excess GnRH secretion - idiopathic or secondary
  • Excess gonadotrophin secretion - pituitary tumour
29
Q

Name the main disorders of gonadotrophin-independent precocious puberty

A
  • Loss of consonance
  • Testotoxicosis
  • McCune Albright
  • Sex steroid secreting tumour or exogenous steroids
30
Q

Describe characteristics McCune Albright syndrome

A
  • Activation of adenylyl cyclase -> hyperactive pathways + over prod of hormones
  • Cafe au lait skin pigmentation
  • Fibrous dysplasia
  • Autonomous endocrine function - most common gonadotrophin-independent precocious puberty
31
Q

Describe characteristics of Testotoxicosis

A
  • Due to activating mutation of LH receptor
  • High levels of testosterone
  • High testosterone causes drop in LH + FSH
  • No FSH -> testis doesn’t grow
  • Appear tall, but small testes
32
Q

What happens in premature adrenarche/pubarche?

A
  • Precocious development of pubic and/or axillary hair
  • Also congenital adrenal hyperplasia / Cushing’s
33
Q

What is premature thelarche?

A
  • Precious breast development
  • Can be unilateral
  • Isolated ‘cyclical’ (<2 yo) with absence of other pubertal development
  • Or variant (>2yo) proceeding to precocious puberty
34
Q

What is pubertal delay?

A

Absence of secondary sexual maturation by 13 in girls (or absence of menarche by 18) or 14 in boys

35
Q

What is the most common type of pubertal delay?

A

Constitutional delay

  • Affects both growth + puberty. Approx 90% of all pubertal delay cases. x10 more common in boys.
  • Secondary to chronic illness eg. diabetes, CF
36
Q

Describe hypogonadotrophic hypogonadism

A
  • Low LH and low FSH
  • Kallman’s syndrome (X-linked KAL gene, GnRH migration - stops production)
  • Other genetic causes eg. hypopituitarism
37
Q

Describe hypergonadotrophic hypogonadism

A
  • High LH and high FSH
  • Gonadal dysgenesis, low sex steroid levels:
  • > congenital - Klinefelter’s or Turner’s
  • > gonadal dysgenesis w/ normal karyotype, viral eg. mumps
38
Q

Describe characteristics and incidence of Klinefelter’s syndrome

A
  • XXY - 1:500 males
  • Frontal baldness absent
  • Poor beard growth
  • Tendency to grow fewer chest hairs
  • Narrow shoulders
  • Breast development
  • Wide hips
  • Long arms + lengs
  • Small testicular size
  • Female-type pubic hair pattern
39
Q

Describe incidence and characteristics of Turner’s syndrome

A
  • XO - 1:3000 girls
  • Being shorter than normal
  • Underdeveloped or ‘streak’ ovaries
40
Q

What is the treatment option for central precocious puberty?

A
  • Case-by-case assessment
  • Decision depends on age, psychological benefits, patients/carers wishes + expectations
  • GnRH analogues to suppress puberty until 11-12 years of age
41
Q

What is the treatment option for hypotrophic hypogonadism?

A
  • V hard to diagnose difference between HH + constitutional delay in childhood (cna’t use gonadotrophins to distuinguish)
  • if HH, gradual increase in sex steroids over 2-3 years

Physiology & Science: Reproduction (18 decks)

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