Histo - Endocrine Organs II
What is Grave's Disease?
hyperthyroidism: thyroid stimulating immunoglobins stimulate thyroid in addition to TSH = continuous stimulation of thyroid occurs
What are the thryoid stimulating immunoglobins and what do they bind to?
antibodies against TSH receptor (IgG)
These antibodies bind to ( ) receptors and elevate levels of ( ). This in turn increases synthesis and secretion of ( ).
TSH receptors, cAMP, T3/T4
What physical changes occur in thyroid gland with Grave's?
hypertrophy/hyperplasia = hyperthyroidism and goiter (enlarged thyroid)
What is exopthalamus?
bulging eyes = sign of Graves's disease
What happens with dietary deficiency of iodine?
hypothyroidism = cannot synthesize thyroid hormone
Why does diffuse enlargement of the thyroid (goiter) result?
no synthesis of T3/T4 due to lack of iodine = no negative feedback to anterior pituatary to inhibit release of TSH
What is Hashimoto's thyroiditis?
inflammation of the thyroid gland causing hypothyroidism
What else can cause hypothyroidism?
How is hypothyroidism treated pharmacologically?
give T4 orally
What do parafollicular (C-cells) secrete?
Where do they arise from?
neural crest cells
What does calcitonin do?
binds to osteoclasts = prevents release of calcium from bone into blood
Does calcitonin have to be given after thyroidectomy? Why?
no: calcitonin has no major effect on blood calcium levels
If you see tumor cells surrounded by extracellular deposition of amyloid in thyroid what is it?
C-cell carcinoma-thyroid medullary carcinoma
What does parathyroid hormone do?
produces parathormone to regulate calcium plasma levels
What do pricipal/chief cells of parathyroid do?
monitor calcium and release PTH
How does PTH stimulate release of calcium from bone?
binds to osteoblasts which in turn stimulate osteoclasts to reabsorb bone and mobilize calcium and phosphate
What does PTH do in renal?
-prevents calcium excretion and promotes phosphate excretion
-also increases calcium absorption in GI tract
excess PTH from parathyroid adenoma or chief cell hyperplasia
What are the symptoms?
-stones: urinary tract stones
-bones: demineralized bones
-groans: pain from stones, fractured bones, and constipation (decreased neuronal excitation)
What are the four layers of adrenal gland and what is the mnemonic?
4 S's: salt, sugar, sex, sympathetic
-z. fasciculta: glucocorticoids
-z. reticularis: androgens
-medulla: norepinephrine and epinephrine
What does z. glomerulosa secrete?
mineralocorticoids: mainly aldosterone
What does z. fasciculta secrete?
What z. reticularis?
norepinephrine and epinephrine
What is aldosterone produced by? Influence?
z. glomerulosa: angiotensin-II
What distinguishes z. fasciculata?
-more cytoplasma and abundant lipid droplets
-cells arranged in parallel plates seperated by capillaries
What does z. fasciculata release and under what influence?
cortisol: under influence of ACTH (exerts negative feedback on ACTH)
What is cortisol needed for?
-normal carb metabolism and maintanence of blood sugar
-maintenance of blood pressure
What do z. reticularis cells secrete? Influene?
androstenedione and DHEA: some influence from ACTH
What is order of cortisol regulation?
CRH to ACTH to Cortisol
When are androstenedione important?
in females (only androgens) but not in males
what happens if there is excess androgens during fetal development?
virilzation in females (enlarged clitoris, fusion of labioscrotal folds)
excess androgens in adulthood?
loss of pubic and axillary hair, decreased libido
What happens to androgens in cushing's?
elevated because ACTH is increased
destruction of adrenal cortex (tuberculosis, autoimmune)
What is lost in addisons?
all adrenal steroids are effected - mineralcorticoids, glucocorticoids and androgens
Adrenal cortical failure can also occur secondary to failure of ( ) secretion. In this case, ( ) are not effected as they are under influence of ( ).
ACTH: mineralocorticoids, RAAS
-excess of ACTH in blood
What is elevated?
ACTH drives cortisol and androgen synthesis/release
What does ACTH do?
drives cortisol and androgen synthesis/release
Besides a tumor, what else can cause cushings?
pharmacological administration of glucocorticoids: in this ACTH will be negatively inhibited by doses of cortisol
Key symptoms cushing's?
buffalo hump, moon face, fat distribution, hypertension, hyperglycemia
What is conn's syndrome?
adenoma of glomerulosa cells = hyperaldosteronemia
What can cause hyperaldosteronemia?
adenoma of glomerulosa cells = XS aldosterone produced
What are pheochromocytes?
modified post-ganglionic sympathetic nerves
when do pheochromocytes stain yellow-brown?
with chromic salts (chromaffin cells)
What activates medullary cells?
sympathetic nerves: fight or flight
What are pheochromocytomas?
tumors of suprarenal medulla: excess catecholamines produced
What do delta cells of pancreas release?
somatostatin: inhibits insulin and glucagon secretion
What permits rapid flow of ions and molecules between pancreatic cells?
What type of capillaries are found in the islet of langerhans?
Which type of diabetes is insulin deficient? Why?
Type I: beta cells of pancreas are destroyed
Which type is insulin resistant diabetes mellitus?
type II: target tissue do not respond to insulin
What are the two cell types of the pineal gland?
pinealocytes and neuroglial cells
What do the secretory granules of pinealocytes contain?
melatonin and serotonin
Melatonin induces rhythmic changes in hypothalamus, adenophysis and gonads in response to ( ).
changes in light received by retina
what is corpora arenacea (pineal sand)?
concentric accretions of calcium and magnesium phosphate in pineal gland