growth hormone

Growth hormone is the most abundant…

anterior pituitary hormone

what kind of cell produces GH?

somatotropes

• the most abundant anterior pituitary cell

• account for at lease half of the total cells

what is the function of GH?

• attainment of normal adult stature

• metabolic role

Metabolic roles of GH

• mobilization of free fatty acids (burn fat)

• inhibits glucose metabolism in muscles and adipose

• increase insulin secretion

• decreases insulin sensitivity

• triggered by gherlin

1920s

scientists studying the pituitary gland’s role in growth regulation

• extracts from the pituitary could stimulate growth

1960s

human growth hormone (hGH) was being used to treat children with growth deficiencies

pituitary glands of cadavers

• limited supple of (hGH) and risky due to contamination concers

• 1985 FDA halted use after cases of Creutzfeldt-Jakob disease (prion disease)

recombinant human growth hormone (rhGH)

• synthesized using genetically modified bacteria

• safe and widely available

Creutzfeldt-Jakob disease (CJD)

rare, fatal neurodegenerative disorder cause by abnormal prion proteins

• leads to progressive brain damage and severe neurological symptoms

CJD features

• rapid progression of symptoms:

  • dementia, memory loss, muscle stiffness, difficulty swallowing

  • atrophy

  • no treatment

where is GHRH released from

growth hormone releasing hormone is released from the hypothalamus

what does GHRH bind

binds to somatotroph in anterior pituitary

growth hormone (GH) is released in anterior pituitary

binds directly to target tissue (JAK-STAT)

• target tissue releases IGF-1

• inhibited by somatostatin

GH does not directly act on tissues

• stimulated the liver to produce insulin-like growth factor (IGF-1) which binds to tissues

• inhibited by somatostatin

• helps take up certain amino acids

• increases lipolysis

growth hormone metabolism muscles

• decrease glucose use

• decrease insulin sensitivity

• increase protein synthesis

• increase fat utilization

growth hormone metabolism liver

• increase gluconeogenesis

• decrease insulin sensitivity

• increase ketogenesis (produce ketone bodies bc of low glucose)

• increase IGF production

growth hormone metabolism adipose tissues

• decrease glucose utilization

• decrease insulin sensitivity

• increase lipolysis

• decrease fatty acid storage

GH increases sensitivity

of beta cells to secrete insulin

• higher conc. of insulin are required to maintain normal glucose

• decrease insulin receptor in fat and muscle

GH stimulates…

protein synthesis in non-fasting individuals

• IGF-1 is produced only in fasting

GH has what kind of effect

pulsatory, spiking throughout the day

• most impactful at night

what inhibits GH release

GH release is feedback inhibited by IGF-1 production from both the liver and bone

GH deficiency causes

• caused by genetic mutations

• pituitary disorders (tumor, trauma, infections)

• congenital defects or. damage to hypothalamus or pituitary

GH deficiency symptoms

in children:

• short stature, delayed puberty, reduced muscle mass

in adults:

• fatigue, decreased bone density, reduced strength, increased fat accumulation

GH deficiency treatment

• GH replacement (rhGH)

• monitoring growth markers

• addressing underlying causes