Endocrinology- Exam 1- Human Growth Hormone

What tissues does human Growth Hormone influence?

-liver, muscle, bone, adipose tissue

What second messengers are used when GHRH stimulates hGH secretion?

(uses both adenylyl cyclase and PLC pathway)

-cAMP

-DAG

-IP3

-Ca2+

What stimulates the release of GHRH?

where are the cell bodies of GHRH primarily located?

How does it circulate and get to the anterior pituitary?

-arcuate nuclei of the hypothalamus

-Hypothalamic-hypophyseal portal system

What does GHRH act on?

What then do these secrete once stimulated?

Somatotrophs-> secrete human growth hormone (hGH)

What stimulates GHRH to be released from the hypothalamus? (5)

- Increased amino acids in blood

- Decrease glucose in blood (hypoglycemia)

-Decrease FA in blood

-Exercise

-Healthy stress

What are all the names for Growth Hormone Inhibiting Hormone (GHIH)

- Growth hormone Release-inhibiting hormone (GHRIH)

-Somatostatin

-Somatotopin release inhibiting factor (SRIF)

What stimulates GHIH/Somatostatin to be released from the hypothalamus?

-Hyperglycemia

-High FA levels

-GH

-Obesity

-Pregnancy

-Senescence

What mechanism of action does GH use?

(explain the process)

tyrosine kinase mechanism

-GH activates the JAK, which activates STAT leading to transcription of target genes to induce proliferation and differentiation of the cell

What is the most important hormone for normal growth into adulthood?

Growth Hormone

T/F: GH is secreted at a constant rate all day

FALSE, bursts every two hours and largest burst w/in 1 hour of sleep

What effect does GH have on adipose tissue?

-increases lipolysis

how does GH effecting adipose tissue increase lipolysis?

-triggers hormone sensitive lipase (HSL) to cut TGs into glycerol and FA (can be used for ATP production)

-Glycerol can then go to the liver to be used for gluconeogenesis

How does GH effect bone?

increase glucose uptake, increase amino acid uptake

GH acting on bone ___________________ protein synthesis, _____________________ bone mineral density, and allows bone to _______________ in _______________.

TQs

increases; increases; grow; length

How does GH effect muscles?

-increase amino acid and glucose uptake

-increase muscle side due to increase protein synthesis

What effect does GH have on the liver? TQ

-increases gluconeogenesis, glycogenolysis and IGF-1 Production (insulin-like growth factor-1)

Some GH will go to the liver to be converted into what?

Insulin-like Growth Factor 1 (IGF-1)

(somatomedin I/ somatomedin C)

IGF-1 binds to insulin receptors to do what? TQ

increase glucose uptake

What effect does IGF-1 have on muscle?

- opens channels for AAs to be taken into the muscle (protein synthesis)

what effect does IGF-1 have on bones? (3)

1. increase osteoblast and osteoclast activity

2. increased endochondral ossification (bigger/thicker bone)

3. increased protein synthesis of Type 1 Collagen

what effect does IGF-1 have on cartilage at the epiphyseal plates?

-increase size, differentiation, proliferation of chondroblasts

-increase linear growth

A growth hormone deficiency (GHD) in children leads to what?

- dwarfism/pituitary dwarfism (too little GH)

GH excess in children lead to what pathology?

-Gigantism (too much GH)

Excess growth hormone (GHD) in adults leads to what?

-Acromegaly

what can cause growth hormone deficiency (GHD) in children? (5)

1. damage to pituitary

2. damage to hypothalamus

3. gene mutation

4. Head trauma

5. Brain tumor

6. Idiopathic (MC)

what complications happen in children with growth hormone deficiency?

- Decreased energy level

-Cardiovascular function risks

-Decreased bone density

What are the symptoms of pituitary dwarfism (caused by deficiency of GH)?

1. immature appearance

2. chubby build

3. prominent forehead

4. puberty late/not at all

5. height growth doesn't meet benchmarks

what is the treatment for growth hormone deficiency? (2)

injections of synthetic GH (can last many years)

what can cause too much growth hormone to be released in children, leading to gigantism?

non malignant tumor of the somatotrophs

What are symptoms of too much growth hormone in children?

large growth during childhood before closure of growth plates

What are some symptoms of too much growth hormone production in children?

-delayed puberty

-vision difficulties

-frontal bossing

-headaches

-increased sweating

-large hands and feet

-weakness

-high prolactin levels (galactorrhea- milk from breast unrelated to childbirth/nursing_

What are the treatments for overproduction of GH in children? (2)

1. remove tumor (if causing problem)

2. Somatostatins to inhibit GH

What causes GH deficiencies in adults?

-damage to pituitary

-surgery

-radiation

-blood supply to pituitary inflicted

complications/symptoms of a deficiency in GH in adults include:

________________bone density

________________muscle mass

________________ sexual function

_______________ body fat (around waist)

________________levels of LDL

decrease; decrease; decrease; increase; increase

what is the treatment for adults with a deficiency of GH?

hGH injections

What occurs when an adult has an excess in GH?

acromegaly

what is the cause of excessive GH in an adult?

non-cancerous tumor (adenoma) in the pituitary gland

What complication arise with an adult having excessive GH?

- swelling of extremities, jaw, nose, supraorbital bulging, tongue, lips etc.

-headaches, blurred vision, voice deepens

-skin tags, profuse sweating, diabetes, dental problems

What is the treatment for adults with excess GH? (3)

-Radiation

-Medication to reduce GH (somatostatin)

-Surgery to remove pituitary gland (hypophysectomy)

what causes lactation in gigantism?

pituitary stalk becomes compressed, disrupting the flow of dopamine to the hypothalamus (which typically inhibits prolactin).

This lack on inhibition leads to secretion of prolactin and milk production

what is milk production in gigantism called?

hyperprolactinemic galactorrhea