33. Growth Hormone and Endocrinology of Growth 2025

What are the two types of effects of GH?

Direct and indirect (via IGF-1)

What are the direct effects of GH?

Stimulates mitosis, protein synthesis, gluconeogenesis, and lipolysis

What are the indirect effects of GH?

Mediated by IGF-1, stimulating cell division and bone/cartilage growth

What is the main site of IGF-1 production?

Liver

What role does IGF-1 play in GH resistance?

Children with GH receptor defects have high GH but low IGF-1

What hormone controls GH synthesis?

GHRH (stimulates synthesis and secretion)

What hormone inhibits GH secretion?

Somatostatin (blocks secretion, not synthesis)

How is GH secretion patterned?

Pulsatile, especially at night in males

What stimulates GH secretion?

Sleep, stress, fasting, exercise, hypoglycemia, amino acids

What pattern of GH secretion is seen in aging?

Decreased amplitude, related to sleep deterioration

How does IGF-1 regulate GH?

Inhibits GH secretion via negative feedback

How does GH stimulate IGF-1 secretion?

Acts on liver and tissues to promote IGF-1 release

What thyroid hormone effect is required for GH action?

Increases GH synthesis and GHRH receptor expression

What is the fetal growth hormone?

Insulin and IGF-II

What happens to linear growth in hypothyroidism?

Severely stunted

What hormone increases during puberty to drive linear growth?

Estrogen

Why do hypogonadal individuals tend to be tall?

Delayed epiphyseal closure

What causes the pubertal GH surge?

Sex steroids (mostly estrogen)

What is the effect of estrogen on bone plates?

Accelerates epiphyseal fusion

Why do aromatase-deficient children fail to grow at puberty?

Androgens can't be converted to estrogen

What hormone opposes GH action in excess?

Glucocorticoids

What is the most common cause of short stature?

Constitutional delay of growth and puberty

What differentiates constitutional delay from familial short stature?

Constitutional delay shows catch-up growth after delayed puberty

What are endocrine causes of short stature?

GH deficiency, GH resistance (Laron’s), hypothyroidism, glucocorticoid excess

What are non-endocrine causes of short stature?

Genetic short stature, malnutrition, chronic disease, psychosocial deprivation

What is Laron’s syndrome?

GH resistance with high GH and low IGF-1

What is psychosocial dwarfism?

Growth failure due to emotional neglect; reversible

What condition causes short stature and dysmorphic features?

Turner syndrome, Prader-Willi, Down syndrome

What lab finding is key in diagnosing GH resistance?

Low IGF-1 despite high GH

What is the cause of gigantism?

GH excess before epiphyseal closure

What is the cause of acromegaly?

GH excess after epiphyseal closure

What are features of acromegaly?

Bone thickening, acral enlargement, jaw protrusion, glucose intolerance

What medication can treat GH excess?

Somatostatin analogs like octreotide

How do you calculate mid-parental height (MPH) in boys?

(Mom’s height + Dad’s height)/2 + 2.5 inches

How do you calculate MPH in girls?

(Mom’s height + Dad’s height)/2 − 2.5 inches

What does a child’s height within 2 SD of MPH suggest?

Likely normal familial variant

What is used to interpret height potential?

Growth velocity, skeletal age, MPH range