Endocrine 3 Flashcards
What is the other name for GH? What is it made of?
Somatotropin
Amino-acid based
Where is GH produced and released?
Anterior pituitary
What are the functions of GH?
metabolic functions (throughout life): fat breakdown increased blood glucose growth functions protein synthesis (muscle mass, cellular growth) bone growth increased cell division
How is GH regulated?
hormonal: GHRH, GHIH from hypothalamus, negative feedback of IGF-I and GH
neural: diurnal rhythms (increase with sleep)
What is an IGF and what does it do in the endocrine system?
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
What is the stimulus in the GH pathway?
GHRH- Growth hormone releasing hormone, from hypothalamus
What are the targets of GH?
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
What hormones provide negative feedback in the GH loop?
IGF’s negative feedback on anterior pituitary
GH negative feedback on anterior pituitary
GHIH (hypothalamus)
What happens with hypersection of GH?
gigantism (whole body enlarged) or acromegaly (enlarged extremities)
What happens with hypo secretion of GH?
Dwarfism- if caught early enough, e.g. before epiphyseal plates close, then can treat with GH (IFF GH-caused)
What are the major thyroid hormones? What kind of solubility?
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
What is the function of T3, T4?
increased metabolic rate, increased heat production, increased growth and CNS development, increased SNS activity (stress)
How are thyroid hormones regulated?
hormonal: TRH (Hypothalamus), TSH (Anterior Pituitary), negative feedback
neural: body temperature, stress
In the thyroid hormone pathway, what is the stimulus?
TRH (hypothalamus)
TSH (anterior pituitary)
What are the targets of thyroid hormone?
all body cells:
increased metabolism & heat production
increased tissue growth and development
blood vessels: increased SNS receptors to maintain blood pressure
What feedback loops do the thyroid hormones use?
Negative feedback to hypothalamus and anterior pituitary
How can thyroid hormones be hormonally inhibited?
GHIH
Dopamine
Glucocorticoids
How can the thyroid hormones be neurally regulated?
By cold- infants
By stress-all
What is T4 made from?
Iodide and tyrosine
How is thyroid hormone synthesized?
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
What is the difference between T3 and T4?
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
What is hyperthyroidism?
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”
What is hypothyroidism?
: 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
What is a consequence of iodine deficiency in kids?
Thyroid hormone deficiency –> can lead to retardation
