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Reproductive System > Puberty And The HPG Axis > Flashcards

Puberty And The HPG Axis Flashcards

1
Q

What is puberty

A

The preparation for sexual maturity

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2
Q

List 4 influences on puberty

A
  • Pineal gland (thought to be an important influence)
  • Body weight in girls
  • Nutrition
  • Leptin (from adipose tissue)
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3
Q

What effect can Pineal Gland disorders have puberty?

What about low body weight?

A

Pineal gland disorders can cause Precocious Puberty (early onset puberty)

Low body weight can cause cessation of menstruation, even after puberty has occurred

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4
Q

What is the Tanner Scale?

What is it based on in boys and girls?

A

A scale used to asses stage of puberty in boys and girls

Boys- Pubic hair and genitalia
Girls- Pubic hair and breast development

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5
Q

Compare Primary and Secondary Sexual characteristics

A

Primary;

  • Sexual characteristics at birth
  • Includes anatomy of internal and external genitalia

Secondary;
- Characteristics that develop after puberty (menstruation, pubic hair, breast/ genital development/ enlargement)

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6
Q

Define;

  • Thelarche
  • Adrenarche
  • Gonadarche
  • Menarche
A
  • Thelarche: Onset of breast development near start of puberty
  • Adrenarche: Maturation and increased activity of adrenal glands prior to puberty
  • Gonadarche: Activation of reproductive glands by FSH and LH
  • Menarche: Onset of menstruation at puberty
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7
Q

At what age range do girls start puberty?

What are the 6 sequence of events?

A

Age 9-13

  1. Thelarche
  2. Initial Pubic hair growth (under influence of testosterone)
  3. Growth Spurt
  4. Menarche
  5. Pubic Hair adult (Becomes coarser, further anatomical spread)
  6. Breast development adult (further growth)
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8
Q

In the Growth Spurt stage of puberty, what are the significance of Oestrogen and Growth Hormone (GH)?

A

Oestrogen: Important in fusion of Epiphyseal Growth Plate, stopping the growth spurt

GH: Key role in causing growth spurt to occur

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9
Q

At what age range do boys start puberty?

What are the sequence of events?

A

Age 10-14

  1. Genital development
  2. Initial Pubic Hair Growth (under influence of testosterone)
  3. Spermatogenesis
  4. Growth Spurt
  5. Genital Enlargement
  6. Pubic Hair Adult
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10
Q

What is the first sign of puberty in boys and girls

A

Boys- Testicular volume enlargement (Genital development stage)

Girls- Initial breast development(Thelarche)

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11
Q

The Growth Spurt stage of puberty occurs much later in boys.

Why do boys typically grow taller than girls?

A

Due to lower oestrogen levels, epiphyseal growth plates close more slowly

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12
Q

When is the HPG axis switched on?

A

Puberty

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13
Q

Explain what effect Precocious Puberty can have on stature

A

Can lead to Oestrogen levels rising earlier-> Shorter stature as Epiphyseal Growth Plates close sooner

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14
Q

What hormone triggers the start of puberty?

What hormone is thought to initially stimulate the Hypothalamus to produce this hormone?

A

GnRH

Leptin is thought to initially stimulate the Hypothalamus to produce GnRH

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15
Q

Describe the HPG Axis

A
  • Hypothalamus releases GnRH to act on Ant. Pituitary Gland
  • Ant. Pituitary Gland releases LH and FSH in BOTH males and females
  • LH and FSH act on Gonads( Ovaries/ Testes) to release Oestrogen and Androgens
  • Oestrogen and Androgens contribute to development of Secondary Sexual Characteristics
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16
Q

Describe the pattern of release of GnRH before and after puberty

A

Before;
- Released in low frequency pulses, especially at night

After;

  • GnRH released every 2 hours in males
  • GnRH release frequency depends on phase of menstrual cycle)
17
Q

Why does GnRH release pattern change after puberty?

A

Before puberty, synapses are not fully matured

18
Q

What cells of the Seminiferous Tubules are acted on by LH and FSH?

A

Sertoli cells- FSH

Leydig cells- LH

19
Q

What will constant administration of artificial GnRH/ GnRH Receptor agonist lead to?

A
  • Reduced sensitivity of GnRH Receptor on AP Gland
  • Leads to reduced FSH and LH release
  • Leads to loss of fertility
20
Q

Is the HPG axis subject to Negative Feedback?

What cells of the developing follicle in ovaries respond to FSH and LH?

A

Yes

FSH- Granulosa cells
LH- Theca Interna cells

21
Q

Sertoli and Granulosa cells respond to FSH

What chemical/ hormone do they produce when stimulated? Why?

A

Produce Inhibin, which causes negative feedback on FSH only

To prevent any further sperm production/ follicle maturation

22
Q

What is Central Precocious Puberty? (Causes early activation of HPG Axis)

List 5 causes

A

Precocious Puberty with elevated GnRH

  • Idiopathic/ Constitutional
  • CNS Lesions
  • Pituitary Gonadotrophin-secreting tumours
  • Systemic conditions (TB)
  • Obesity related precocious sexual development due to increased Leptin levels
23
Q

What is Peripheral Precocious Puberty? (Causes early activation of HPG Axis)

List 5 causes

A

Precocious puberty without elevated GnRH

  • Increased androgen production
  • Increased oestrogen production
  • Increased Beta-HCG production
  • Primary hypothyroidism
  • Obesity-related early sexual development due to compensatory hyper insulin anemia (due to obesity)
24
Q

How do Oestrogen/ Testosterone and FSH/LH levels differ in Central and Peripheral Precocious Puberty?

A

Central;

  • Raised oestrogen/ testosterone
  • Raised LH and FSH

Peripheral;

  • Raised oestrogen/ testosterone
  • Decreased LH and FSH (Negative feedback on GnRH from Oestrogen and Testosterone)
25
Q

Define Delayed onset of puberty

List 3 causes

A

Absent/ incomplete development of secondary sex characteristics by age of 14 in boys/ 13 in girls

  • Hypogonadism
  • Malnutrition/ other chronic diseases (Hypothyroidism)
  • Constitutional Growth Delay (most common)
26
Q

What is Constitutional Growth Delay?

What’s the cause?

A
  • Temporary delay in growth and onset of puberty, not caused by any pathological process
  • Inherited as Autosomal Dominant/ Recessive or X linked
27
Q

How is Constitutional Growth Delay diagnosed and treated?

A

Diagnosis: X-ray showing a bone age less than individuals’s age

Treatment: None needed, catch up-growth eventually occurs and normal height reached

28
Q

Most parts of Reproductive system can work before puberty

Why don’t they?

A

Due to low GnRH levels

Reproductive System (21 decks)

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