Puberty and Aging

Question 1

What is puberty?

Answer 1

: The transition from sexual immaturity to fertility during with secondary sexual characteristics develop (transition from childhood to adolescence)
- Reproduction is possible once full activation of reproductive signalling is achieved

• Involves the progressive activation of the HPG axis and the development of secondary sexual characteristics
• The initiating factors are still mostly unknown

Question 2

What are the first visible signs of puberty in males?

Answer 2

• Testicular volume of 4 mls

Question 3

What Tanner Stages encompass puberty in males?

Answer 3

• Stages II to V

Question 4

What factors affect the timing of puberty?

Answer 4

• Primarily determined by genetics
• The most significant environmental factor is nutritional status in childhood
  i. e. underweight children often experience delayed puberty
  i. e. the critical weight theory is that the body weight of a child is the driving factor in the initiation of puberty

Question 5

What is precocious puberty?

Answer 5

• Development of secondary sexual characteristics before the age of 8 in girls and 9 in boys

Question 6

What is adrenarche?

Answer 6

• The onset of adrenal steroid production specifically the production of DHEA and DHEAS
• DHEA can act as precursors for the productions of more potent androgens such as testosterone
• What triggers adrenarche is unknown
• Adrenarche precedes puberty
• The phenotypic hallmark of adrenarche is androgen dependent growth of axillary and pubic hair

Question 7

Describe GnRH pulsatility changes throughout puberty:

Answer 7

Pre-pubertal:

• Restraint is imposed on pulsatile GnRH release
• Gonadostat theory: during childhood the hypothalamus is highly sensitive to negative feedback
• FSH and LH are very low

Early Puberty:
- Sleep associated increases in LH pulse frequency

Late Puberty:
- Sleep associated LH pulse frequency decreases so it resembles day time frequency

Question 8

Describe the kisspeptin theory of puberty initiation:

Answer 8

• Prior to puberty the kisspeptin receptor is expressed on the surface of GnRH neurons but no kisspeptin is present
• During early puberty there is the emergency of kisspeptin inputs to the GnRH neuron
• It is thought that the onset of kisspeptin synthesis is driven by factors such as GABA and glutamate
• Maturations of the electrical response of GnRH neurons to kisspeptin occurs during puberty

Question 9

What is menopause?

Answer 9

• Permanent cessation of menstruation resulting from a loss of ovarian function occurring in women aged over 45
• The average age is 51
• Perimenopause is the 2-8 years preceding menopause and the 1 year after the final menstrual period
• Menopause involves the complete depletion of the ovarian reserve and significant changes in hormone levels including a decrease in estrogen and inhibin B and an increase in FSH and LH

Question 10

What is andropause?

Answer 10

• The decline of testosterone levels in men >50 years of age
• Loss of high amplitude LH pulses
• Decreased responsiveness of the Leydig cells to LH
• Due to decrease in testosterone there is an increase in basal LH levels