Human Growth Hormone

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Term for - syndrome that results when the anterior pituitary gland produces excess GH after epiphyseal plate closure at puberty. A number of disorders may increase the pituitary's GH output, although most commonly it involves a tumor called pituitary adenoma, derived from the somatotrophs.

Acromegaly

DA is produced where?

Arcuate nucleus

GHRH is produced where?

Arcuate nucleus

What improves genetic predicatibility of human growth?

Being well nourished

Why can IGF-1 injection cause hypoglycemia?

Cause high dose can cross react with insulin receptors in muscle

Whats Laron Syndrome

GH receptor disorder - high GHRH, low IGF-1, high GH - short stature

What is insulin's involvement in growth

Growth factor especially in utero and in children

What is IGF-2's involvement in growth

Growth promoting hormone during gestation. "Major fetal growth factor"

Whats the difference between hypothyroid dwarfs and non-hypothyroid dwarfs

Hypothyroid - maintain infantile proportions non-hypothyroid - develop adult proportions just in a smaller size

GH reuglates post-natal growth mostly via ________

IGF-1

Pigmies are unable to produce what?

IGF-1

What stimulates proliferation and differentiation of chondrocytes (bone growth)

IGF-1

What stimulates proliferation and differentiation of myoblasts to grow muscle

IGF-1

Which hormone is critical for intrauterine growth

IGF-1

IGF-1 is structurally similar and can cross react with what molecules

IGF-2 and inuslin

Term for - autosomal recessive disorder characterized by an insensitivity to growth hormone (GH), caused by a variant of the growth hormone receptor. It causes short stature and a resistance to diabetes and cancer

Laron's Syndrome

Term for - a rare lethal familial condition marked by slow physical and mental development, wide-set eyes, low-set ears, hirsutism, and severe endocrine disorders, such as enlargement of the clitoris and breasts in females and of the phallus in males.

Leprechaunism or Donohue's Syndrome

What is made in adipocytes taht acts on the arcuate nucleus to give sensation of satiety

Leptin

Failure to treat a hypothyoroid state in a child will result in what? What if you treat it later?

Mental retardation and slow growth Growth will catch up but mental effects are permanent

GHRH stimulates what cells to secrete GH

Somatotrophs

Whats another name for growth hormone

Somatotropin

Describe regulation of GH

Stimulated by: GHRH Ghrelin DA opposing SST Inhibited by: SST IGF-1 GH itself feeds back to inhibit GHRH and stimulate SST

What is true regarding use of GH as performance enhancing drug

Strong evidence shows GH has no effect on muscle mass or strength. Some evidence that combined with testosterone it has some affect

What effects do GC's have on growth rate

They slow development of chondrocytes - so growth will slow, but there will be catch up growth after removal of the GC's

Satiety center is located where? What about hunger center?

Ventromedial nucleus Lateral hypothalamic area

What is the role of androgens and estrogens in growth

Very important in pubertal growth spurt -- too much leads to faster growth but smaller window and shorter stature

What is thyroid hormones involvement in growth

important for in utero and early childhood development

Bone growth occurs where? By what cells?

Epiphyseal Plates Chondrocytes

GH activates receptors to use what pathway

JAK/STAT

IGF-1 half life is what

15-20 mins

Whats the dominant form of GH

22kDa form

What causes females growth to plateau earlier than males

Estrogen closing epiphyseal plates

Term for - a condition of severely stunted physical and mental growth due to untreated congenital deficiency of thyroid hormones

Cretinism

What can cause fetal macrosomy?

Diabetic mother with high insulin leading to high birth weight

What are the 2 distinct effects of GH

Direct - increasing metabolism of proteins, lipids, and glycogen Indirect - promoting growth effects through stimulating IGF-1 production by liver and most tissues

SST is produced where?

Dorsomedia lnucleus

What are the major hormonal determinants of linear growth in normal post-uterine life

GH and IGF-1

Describe GH effects on muscle glucose uptake, lipolysis, and gluconeogenesis

Increases gluconeogenesis decreases uptake increases lipolysis makes tissues insulin resistant

What are the locations of IGF-1 feedback?

Inhibits somatotrophs Inhibits GHRH release in arcuate nucleus Increases SST release from dorsomedial nucleus

Most of pulsatile GH release is when? What can increase GH release?

Night time Exercise, stress, high protein meal, fasting

Is human growth linear?

No - it is episodic, w/ major growth events as an infant and in puberty

Does IGF-1 handle all growth effects?

No GH has some effects that are not well known

Whats the most important extrinsic factor affecting growth

nutrition

How much of human heigh is genetic and how much is nutrition

probably 60-80% genetic 20-40% nutrition

Children with diabetes have faster or slower growth rates

slower - insulin is a growth factor

IGF-1 acts through what signaling pathway

tyrosine kinase receptor


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