Childhood growth and puberty Flashcards
The most rapid growth occurs during the _______ phase
in utero
What drives growth during fetal life?
IGF-1, insulin
What drives growth during childhood?
growth hromone
What drives growth during infancy?
nutritional status
What drives growth during the pubertal growth spurt?
stimulation of growth plate by androgens, estrogen, GH
List factors that stimulate GH secretion
GHRH
estrogen and androgens enhance GH response to GHRH
What factors inhibit GH secretion
somatostatin
high levels of glucocorticoids
GH and IGF-1 feedback, which increases somatostatin
What might explain the poor correlation of total IGF-1 levels with growth?
circulating IGF-1 is likely not the most important mediator of GH effect- GH stimulates local production of IGF-1 in tissues, which exerts an autocrine growth promoting
effec
Describe the effects of GH and IGF-1 on bone
GH: linear growth by action at epiphyseal growth plate
Describe GH effects on adipose tissue
utilization of fat for energy, sparing lean body mass
increase synthesis of hormone sensitive lipase (hydrolyzes TGs)
inhibits lipoprotein lipase
Describe GH effects on muscle
increased muscle mass, increased protein synthesis
Describe GH effects on carbohydrate metabolism
insulin resistance and glucose sparing
Differences in childhood _______ largely determine differences in adult height
growth velocity
disparity in heights of children at start of puberty= disparity in height in adulthood
Growth velocity is most rapid in utero and during the first year of life, when ______ factors predominate
nutritionally- derived, ex insulin
As the transition to GH dependent growth occurs, growth velocity ________
decreases
The greater the delay in the onset of puberty, the _______ the pre-pubertal growth rate
slower
Crossing of growth percentiles is common during _______ years of life
first 2 years- baby “seeks out” appropriate growth channel based on genetics
not normal to cross percentile lines from age 3- adolescence
What growth pattern is suspected if:
- growth velocity is steady along low percentile lines
- bone age= chronological age
intrinsic short stature
check MPH to verify
If a child has intrinsic short stature but is significantly smaller than predicted by MPH, what causes should be considered?
mild hypochondroplasia
chromosomal disorders- Turners
in utero insults
What growth pattern is suspected if:
- growth velocity along low percentile lines
- bone age
constitutional delay of growth and puberty
What causes short stature during childhood in constitutional growth delay?
transition from the rapid growth phase of infancy to the slower growth of childhood occurs much earlier than normal
- expect crossing down of percentiles at 10-30 months
In ________ growth pattern, growth velocity is abnormally slow
attenuated
What are some causes of attenuated growth pattern
- nutritional deficiencies
- chronic disease
- severe emotional disorders
- medications- corticosteroids, methylphenidate
Hormonal alterations tend to cause marked retardation in linear growth with what effects on weight?
continued weight gain- usually stays along the same weight percentile
Accelerated growth is usually associated with _______
obesity
Why are infants with GH deficiency usually a normal size at birth
GH is not critical for in utero growth
What clinical signs might indicate Gh deficiency
multiple midline defects including cleft palate, poor development of nasal bridge
cherubic faces
lack of phallic growth in males
What are some FDA approved uses for GH therapy
- GH deficiency
- Turner, Prader-Willi
- IUGR
- chronic renal insufficiency
Define gonadarche, thelarche, adrenarche, menarche
- gonadarche: maturation of testes or ovaries to produce hormones
- thelarche: breast budding (nl-10 yrs)
- adrenarche: maturation of adrenal gland (age 6-8 yrs)
- menarche: normal is about 12 yrs
What are the findings in premature thelarche?
Early breast development without growth acceleration, bone age advancement, other signs of puberty
Describe transient gynecomastia common in boys
breast development- high testosterone in puberty is aromatized to estradiol, stimulates temporary growth in breast tissue
What are the findings in premature adrenarche?
early maturation of adrenal gland, but no gonadal changes so no bone advancement, acceleration in growth velocity
________ is a hypothalamic protein that signals GnRH pulses to begin in puberty
kisspeptin
What is the current definition of precocious puberty?
hanges occurring before the age of 7 to 8 years in girls and 9 years in boys
What is the current definition of delayed puberty?
For girls, no thelarche by age 14 or menarche by age 16 years.
For boys, no testicular changes by age 15 years
Describe the two categories of delayed puberty
Hypogonadotropic: Low LH and FSH, due to CNS defect.
Hypergonadotropic: High LH and FSH, due to defect in gonad.
What are some causes of hypogonadotropic delayed puberty?
hypothalamic or pituitary disease, malnutrition, chronic disease, familial syndromes, and endocrine diseases.
What are some causes of hypergonadotropic delayed puberty?
chemotherapy, radiation, trauma, inflammation, or infiltration of the gonads, and chromosomal disorders such as Turner syndrome.
Differentiate central vs peripheral precocious puberty
CPP is caused by premature activation of the HP axis. Gonadotropins are in pubertal ranges.
PPP is not under the control of the central nervous system. Can arise in a gonad, a tumor, or another organ. Gonadotropins are low- suppressed by feedback from the abnormal sex hormone production
How is CPP diagnosed?
increased LH/FSH secretion in response to GnRH stimulation testing
How is CPP treated?
long acting GnRH analogs, which stop pulsatile release
What is McCune-Albright syndrome?
G-protein activating mutation that can present as PPP, Cushing syndrome, or thyrotoxicosis.
Children have characteristic caféau- lait macules, polyostotic fibrous dysplasia, rapid growth
What is familial testotoxicosis?
male disorder with penile enlargement, pubic hair, behavior problems
due to constitutively active LH receptor
