Endocrine 3

Question 1

What is the other name for GH? What is it made of?

Answer 1

Somatotropin

Amino-acid based

Question 2

Where is GH produced and released?

Answer 2

Anterior pituitary

Question 3

What are the functions of GH?

Answer 3

metabolic functions (throughout life):
fat breakdown
increased blood glucose
growth functions
protein synthesis (muscle mass, cellular growth)
bone growth
increased cell division

Question 4

How is GH regulated?

Answer 4

hormonal: GHRH, GHIH from hypothalamus, negative feedback of IGF-I and GH
neural: diurnal rhythms (increase with sleep)

Question 5

What is an IGF and what does it do in the endocrine system?

Answer 5

Growth hormones actions to promote growth are mediated by IGF’s (insulin-like growth factors), also called somatomedins
IGF’s: peptide hormones
IGF-I: mainly released into blood by liver, local production by individual tissues
stimulates soft tissue cell number and cell size
stimulates long bone growth
negative feedback to anterior pituitary to decrease GH
IGF-II: fetal development, adult role unknown

Question 6

What is the stimulus in the GH pathway?

Answer 6

GHRH- Growth hormone releasing hormone, from hypothalamus

Question 7

What are the targets of GH?

Answer 7

liver: produce IGF’s, breakdown glycogen glucose
stimulates soft tissue cell number and cell size
stimulates long bone growth
adipose tissue: breakdown fats  fatty acids
all body cells: growth and metabolism, increase amino acid uptake & protein synthesis, reduce glucose uptake (more glucose in blood), increase fatty acid uptake

Question 8

What hormones provide negative feedback in the GH loop?

Answer 8

IGF’s negative feedback on anterior pituitary
GH  negative feedback on anterior pituitary
GHIH (hypothalamus)

Question 9

What happens with hypersection of GH?

Answer 9

gigantism (whole body enlarged) or acromegaly (enlarged extremities)

Question 10

What happens with hypo secretion of GH?

Answer 10

Dwarfism- if caught early enough, e.g. before epiphyseal plates close, then can treat with GH (IFF GH-caused)

Question 11

What are the major thyroid hormones? What kind of solubility?

Answer 11

T3 and T4 are the major metabolic hormones of the body
lipid-soluble, plasma protein bound
T4: tetra-iodothyronine; stored and secreted form
T3: tri-iodothyronine; more potent, biologically active form

Question 12

What is the function of T3, T4?

Answer 12

increased metabolic rate, increased heat production, increased growth and CNS development, increased SNS activity (stress)

Question 13

How are thyroid hormones regulated?

Answer 13

hormonal: TRH (Hypothalamus), TSH (Anterior Pituitary), negative feedback
neural: body temperature, stress

Question 14

In the thyroid hormone pathway, what is the stimulus?

Answer 14

TRH (hypothalamus)

TSH (anterior pituitary)

Question 15

What are the targets of thyroid hormone?

Answer 15

all body cells:
increased metabolism & heat production
increased tissue growth and development
blood vessels: increased SNS receptors to maintain blood pressure

Question 16

What feedback loops do the thyroid hormones use?

Answer 16

Negative feedback to hypothalamus and anterior pituitary

Question 17

How can thyroid hormones be hormonally inhibited?

Answer 17

GHIH
Dopamine
Glucocorticoids

Question 18

How can the thyroid hormones be neurally regulated?

Answer 18

By cold- infants

By stress-all

Question 19

What is T4 made from?

Answer 19

Iodide and tyrosine

Question 20

How is thyroid hormone synthesized?

Answer 20

Thyroglobulin with tyrosines synthesized in follicular cells
iodide actively transported into follicular cells
iodide converted to iodine
iodine attached to tyrosine in colloid
T3 and T4 made in colloid by attaching to thyroglobulins
T3-thyroglobulins and T4 – thyroglobulins back into follicular cells
T3 and T4 cleaved from thyroglobulins diffuse into blood

Question 21

What is the difference between T3 and T4?

Answer 21

T4 major form stored/secreted, the major form in bloodstream
Converted in liver/kidney
Some T3 made by thyroid
T3 is the one we need, 10x more potent, biologically active form

Question 22

What is hyperthyroidism?

Answer 22

excess T3 and T4 due to autoimmune disease, tumors. In adults causes high metabolism, sweating, tachycardia, irregular heartbeat, anxiety, protruding eyeballs
Grave’s disease (autoimmune)
“feel hot and anxious”

Question 23

What is hypothyroidism?

Answer 23

: low T3 and T4 due to lack of iodine in diet, TRH/TSH deficiency, thyroid gland disease in adults causes low metabolism, cold, sluggish, dry skin, puffy eyes, edema
myxedema, cretinism (mental disability)
goiter: enlarged thyroid gland due to iodine deficiency

Question 24

What is a consequence of iodine deficiency in kids?

Answer 24

Thyroid hormone deficiency –> can lead to retardation