Male Puberty

Question 1

Describe the basic events that occur with the gonads during gestation

Answer 1

Early in gestation germ cell migration begins and sertoli and Leydig cells begin to be produced from a gonad. Sertoli cells form seminiferous tubes and secrete AMH to cause regression of Mullerian ducts, while Leydig cells are stimulated by placental hCG and secrete testosterone and INSL3. By week 11 all testicular components are present, sertoli cell masses continue to increase, and the testicles descend to the inguinal ring at 14 weeks and then to the scrotum at 35 weeks.

Question 2

What is the minipuberty experienced by newborns?

Answer 2

There is a rapid rise in testosterone up to 400nd/dL in the first day of life that declines rapidly during the first week to 20-50, then increases over the first 2 months postnatally (this occurs due to transient activation of the HPG axis before CNS inhibition is fully mature). The levels then decline again to prepubertal levels by 1 yr.

During this minipuberty, FSH levels are higher than LH and penile length increases

Question 3

Question 4

What are some factors that suppress GnRH pulsatile release after the minipuberty until puberty?

Answer 4

• GnRH
• NPY
• GABA
• Leptin
• TGF-a

Question 5

What is Kisspeptin?

Answer 5

A protein believed to be responsible for allowing pulsatile release of GnRH for the onset of puberty. This protein binds to GPR54 receptors on the GnRH neuron body to allow release from the axonal body.

Other stimulatory molecules include leptin, glutamate, and norepinephrine

Question 6

T or F. GPR54 (the receptor for kisspeptin) is sensitive to GnRH antagonists

Answer 6

T. So it will be turned off as well

NOTE: GPR54 and kisspeptin have increased expression at the time of puberty (maximal expression)

Question 7

Puberty is marked by the increase in the pulse frequency and amplitude of GnRH, increase in FSH and LH pulses, and rise in gonadal hormones

Question 8

What neurotransmitters stimulate the HPG axis at the onset of puberty? Inhibit?

Answer 8

Stimulate- GlutamateInhibit- GABA

Question 9

T or F. Changes in expression of tumor suppressor genes like Oct-2, EAP-1, TTF-1 are permissive for puberty onset

Answer 9

T.

Question 10

What is Williams Sydrome?

Answer 10

Deletion of 7q11.23 results in normal onset of puberty with rapid progression (point: Genes contiguous with elastin affect pace of puberty)

Question 11

Signaling through which parts of the hypothalamus are inhibitory to the onset of puberty? Stimulatory?

Answer 11

–Inhibitory tracts appear routed through the posterior hypothalamus

–Stimulatory tracts appear routed through the anterior hypothalamic preoptic area

Question 12

What is Anosmia?

Answer 12

lack of normal sense of smell

Question 13

What are some genes that when upregulated inhibit the release of GnRH and the onset of puberty?

Answer 13

–GnRHR

–KAL-1

–FGFR-1

–GPR54

–LHX3

Question 14

What does mutation in KAL-1 cause?

Answer 14

Clinically, mutation results in the X-linked form of Kallmann syndrome. Individuals with Kallmann syndrome experience anosmia (lack of smell) and do not go through puberty (hypothalamic hypogonadotropic hypogonadism).

Question 15

How is leptin involved in puberty control?

Answer 15

Leptin is secreted by fat cells and in addition to increasing insulin sesnitivity and satiety, acts on the hypothalamus to stimulate GnRH secretion. Thus, deficiency (commonly in very athletic young females with low body fat) can delay puberty. Similarly, prolonged excess of leptin in obese children down regulates GnRH release so delayed puberty can be seen in fat children as well

Question 16

The HPG axis reaches its nadir at what age?

Answer 16

around 6 years old. Even during the mini=puberty, when there is incomplete suppression of the axis, LH/FSH levels are still very low and it is extremely rare to see sexual development

Question 17

What is the earliest change seen in late preadolescence before the onset of puberty?

Answer 17

Earliest change is rise in DHEA-S from adrenals

Question 18

What are some other changes that occur in late preadolescence?

Answer 18

• There is change in amplitude and then frequency of discharge of the GnRH pulse generator
• Results in a sleep-related increase in LH
• Overall there is a 25 fold rise in LH over the course of pubertal development
• LH response is more robust than the FSH response to GnRH and the LH:FSH ratio increases on stimulation

Question 19

What is a stadiometer?

Answer 19

height measurement device (measure 3x and take an average)

Rules: shoes off, heels together, legs straight, dick out

Question 20

What is an orchidometer?

Answer 20

Measures testicular size using beads ranging in size

Question 21

What is the earliest sign of puberty in males?

Answer 21

enlargement of the testes to 4mm

Question 22

How much of human height is based on genetics?

Answer 22

85%

Question 23

What is the eqn for midparental height (genetic growth potential) in boys?

Answer 23

• MPH = [father Ht + (mother Ht + 13)]/2 (centimeters)
• MPH = [father Ht + (mother Ht + 5.07)]/2 (inches)
• Average height velocity examples:

–Age 3: ~8 cm/year

–Age 10: ~5 cm/year

–Peak of pubertal growth spurt: ~10 cm/year

Question 24

What is the eqn for midparental height (genetic growth potential) in girls?

Answer 24

• MPH = [(father Ht-13) + mother]/2 (centimeters)
• MPH = [(father Ht-5.07) + mother]/2 (inches)

Question 25

Question 26

T or F. The minpuberty of infancy typically does not have testicular enlargement

Answer 26

T.

Question 27

Question 28

Answer 28

Question 29

Answer 29

Question 30

Tanner 2 PH

mean lower limit

Caucasian 12y 9y

African Am 11.2y 8y

Mexican Am 12.3y 9.5y

Question 31

What is constitutional delay?

Answer 31

AD disorder more common in boys in which the age of onset of puberty is delayed by an average of 2.5 years in girls and 3 years in boys

In this variant of normal growth, linear growth velocity and weight gain slows beginning as young as age 3–6 months, resulting in downward crossing of growth percentiles, which often continues until age 2–3 years. At that time, growth resumes at a normal rate, and these children grow either along the lower growth percentiles or beneath the curve but parallel to it for the remainder of the prepubertal years.

At the expected time of puberty, the height of children with CDGP begins to drift further from the growth curve because of delay in the onset of the pubertal growth spurt. Catch-up growth, onset of puberty, and pubertal growth spurt occur later than average, resulting in normal adult stature and sexual development. Although CDGP is a variant of normal growth rather than a disorder, delays in growth and sexual development may contribute to psychological difficulties, warranting treatment for some individuals. Recent studies have suggested that referral bias is largely responsible for the impression that normal short stature per se is a cause of psychosocial problems; nonreferred children with short stature do not differ from those with more normal stature in school performance or socialization.