Disorders of Puberty Flashcards
Describe the hypothalamic axis for sex hormones.
- Hypothalamus secretes GnRH in a pulsatile manner
- This stimulates the anterior pituitary to release LH, FSH
- This stimulates the gonads (ovaries/testes) to secrete progestrone/estrogen/testosterone
Describe the activity levels of the hypothalamic sex hormone axis over time
- HPG axis is active in fetal development and infancy (mini-puberty)
- HPG axis then becomes dormant during “juvenile pause” due to inhibitory neurotransmitters acting on hypothalamus
- HPG re-activates during puberty
What stimulates the hypothamus to re-awaken after juvenile phase?
KISS-1 neuron
Compare the levels of FSH and LF before and during puberty
Prepuberty: FSH > LH
Puberty: LH > FSH
Describe two laboratory evaluations of puberty
- Serum sample of LH, FSH
- High levels confirm puberty, low levels cannot rule puberty out (may have missed a pulse)
- If LH/FSH was low, give GnRH analog and measure LH/FSH response
- If child is not in puberty yet, GnRH will not have an effect (no change in LH, FSH)
- If child is in puberty, FSH and LH will rise
Estrogen stimulates… (4)
- Breast development
- Growth/maturation of uterus, vagina, and labia
- Female fat distribution
- Menses
Testosterone stimulates…(4)
- Penile and prostate growth
- Pubic hair
- Muscle mass
- Voice change
*This all follows enlargement of testes (mediated by FSH, LH)
What causes bone age advancement?
Estrogen!
This is the case for both boys and girls
Define adrenarche.
What does this cause? (3)
Adrenarche = when adrenal glands start producing androgens (DHEA, androstenedione)
This causes pubarche (pubic/axillary hair, body odor, and acne)
What is the diagnostic criteria for delayed puberty?
- Onset of puberty after
- 13 years in girls
- 14 years in boys
- OR lack of progression (no menarche/genital growth a few years after starting puberty)
What will best indicate the expected onset of puberty?
Bone age
This best represents the body’s physiologic age
What is Hypogonadotropic Hypogonadism?
Lack of puberty due to decreased GnRH or LH/FSH
(central)
Describe the growth course in Constitutional Growth Delay (3)
- Growth decelerates in first 2 years, which puts child on a low percentile growth curve
- Normal linear growth at this lower percentile
- Onset of puberty is late, but corresponds with bone age (bone age is delayed)
Name 2 genetic causes of Hypogonadotropic Hypogonadism
Prader Willi
Kallman Syndrome
What is the pathogenesis of Kallman Syndrome?
What are the two primary symptoms?
- Defective migration of GnRH-releasing neurons and the olfactory bulb, causing low GnRH synthesis in the hypothalamus
- Sx: anosmia, hypogonadotropic hypogonadism (infertility, failure to complete puberty)
What would GnRH, LH, FSH, estrogen, and testosterone level by in hypergonadotropic hypogonadism?
- Elevated GnRH, LH, FSH
- Low estrogen/testosterone
*This is primary gonadal failure
What is the underlying abnormality in Klinefelter’s?
Name 4 signs/symptoms
- 47, XXY
- Learning disabilities
- Eunuchoid body shape (tall, long extremities, gynecomastia, female hair distribution)
- Testicular atrophy
- Infertility
What is the treatment of hypogonadism?
Hormone replacement (testosterone or estrogen+progesterone)
What would GnRH, LH, FSH, and testosterone levels be in Kallman syndrome?
They would all be low b/c the problem is in the hypothalamus.
Describe the defect in placental aromatase deficiency.
What are two symptoms?
- Inability to synthesize estrogens from androgens (due to aromatase defect), leading to high levels of androgens
- Sx: Masculinization of female (46,XX) infants or maternal virilization
Describe the hormones produced due to LH and FSH stimulation
- LH stimulates Leydig cells
- Leydig cells make testosterone
- FSH stimulates Sertoli cells
- Sertoli cells make androgen binding protein, aromatase, inhibin, anti-mullerian hormone (SAANA)
Describe the labs seen in Klinefelters related to Leydig and Sertoli dysgenesis.
- Dysgenesis of seminiferous tubules -> abnormal Sertoli cells -> low inhibin levels -> high FSH
- Abnormal Leydig cells -> low testosterone -> high LH -> high estrogen
