Endocrine Flashcards
Describe 3 zones of adrenal gland and what they produce
Outer: zona glomerulosa (salt) - mineralocorticoids = aldosterone
Middle: zona fasciculata (sugar) - glucocorticoids
Inner: zona reticularis (sex + steroids) - androgens, estrogens, epinephrine / norepinephrine (from Chromatin cells)
What are effects of norepinephrine on alpha / beta receptors?
alpha - cause vasoconstriction through increased resistance - increase SAP
beta 1 - increase force contraction & increase HR
Describe arterial and venous supply to thyroid glands & innervation
Cranial thyroid a (1st off carotid) –> runs dorsal
Caudal thyroid a (brachiocephalic) –> caudal pole
– both anastomose then bifurcate and enter medial / lateral
Cranial thyroid v –> internal jugular at caudal larynx
Caudal thyroid v –> Internal jugular at caudal neck
** NO CAUDAL THYROID A IN CATS
Cranial laryngeal n. (from vagus n.)
What are the arterial / venous supply of adrenal glands?
Phrenicoabdominal a, renal a, cranial abdominal a
R adrenal v –> caudal vena cava
L adrenal vein –> Left renal vein
Location of external / internal parathyroids?
Vascular and nerve supply?
External –> cranial, not part of parenchyma
Internal –> within, at caudal pole
External - brach of cranial thyroid a
Internal - vessels surrounding parenchyma
Nerve - cranial laryngeal n.
Describe pathway of RAAS and how it creates aldosterone
Renin (juxtaglomerular apparatus kidney) –+ Angiotensinogen (from liver) –> Angiotensin I (in blood)
Angiotensive converting enzyme –+ Angiotensin I –> Angiotensin II (in pulmonary capillaries)
–> vasoconstriction + (+) aldosterone secretion (zona glomerulosa) –> Na/Cl/H2O absorption, K+ excretion by renal tubules
Where is PTH made, by what cell, and describe its effects to adjust Ca/P
Where is calcitonin made and what does it do?
PTH is synthesized by Chief cells
Bone - increases Ca/P resorption
Kidney - decreases Ca excretion, increases P excretion
Kidney - increases 1,25 dihydroxycholecalciferol from Vit D (calcitriol) –> works on Intestine - increase absorption of Ca/P
Calcitonin - made in thyroid “C” cells
- Prevents hypercalcemia, decreases bone resorption
Where is ectopic thyroid or parathyroid tissue found?
TH: trachea, thoracic inlet, mediastinum, descending aorta (thorax)
PTH: 3-6% of dogs - thymus; detected histologically in 35-50% of cats
Describe the effects of epinephrine on the various receptors
Epinephrine ~10x more potent on beta-2 receptors than norepinephrine - more important in controlling metabolism
Beta 2 - vasodilation of skeletal mm arterioles, coronary arteries, and all veins
Beta 2 - promotes glycogenolysis & gluconeogenesis (liver & skeletal mm) - forms lactate –> Increase BG concentrations
Alpha 2 - inhibits insulin secretion
Alpha 2 - stimulates glucagon secretion
Beta 1 - heart - increases force contraction & increases heart rate (shortens diastole depolarization)
Describe pathway to make thyroid hormone & which are biologically active
Thyroglobulin produced (precursors for TH)
- stored in lumen
- once iodine available –> goes into follicular cell –> hydrolyzed into thyroxine (T4) and triiodothyronine (T3) –> blood
- T4 & T3 mostly bound
- T4 major secretory; T3 major biologic activity
Hypothalamus - Thyrotropin Releasing Hormone TRH –> pituitary –TSH –> thyroid - Thyroid hormone TH
TSH secretion is inhibited by TH in negative feedback loop
How are catecholamines formed?
Rate of Norepi/epi in cats vs dogs?
Where are the alpha 1, alpha 2, beta 1, beta 2 receptors?
Catecholamines from tyrosine / phenylalanine via tyrosine hydroxylase
Cats: 70% epi / 30% Norepi
Dogs: 60% epi / 40% NE
Alpha 1 - presynaptic endings
Alpha 2 - postsynaptic endings
Beta 1 - heart
Beta 2 - metabolism & smooth mm contraction
Name the (+) and (-) functions of glucocorticoids
+ hepatic gluconeogensis
+ lipolysis
+ protein catabolism
+ GFR
+ gastric acid secretion
- glucose uptake / metabolism in tissues
- protein synthesis
- vasopressin
- inflammatory response / immune system
- glucocorticoid production (negative feedback)
–> overall increases Glucose in bloodstream
- What size usually says adrenal is “too large”?
- What are guidelines for malignancy on CT vs US?
- What is accuracy of CT to ID vascular invasion?
- What % of Cushing’s have pituitary form?
- 1.5 cm or greater
- Mass size (>20 mm); invasion of mass into surrounding tissues and BVs; identification of additional mass lesions
- 95% accurate
- 80-85% (80% to 85% of dogs with naturally occurring hyperadrenocorticism have the pituitary-dependent form (pituitary-dependent hyperadrenocorticism) - excessive secretion of ACTH by the pituitary gland causes bilateral adrenal hyperplasia and excessive glucocorticoid secretion)
- Between pituitary dependent & adrenal dependent Cushing’s, which shows suppression of cortisol with LDDST?
- What % of pituitary do / don’t suppress?
- What are diagnostic tests to test for pheochromocytoma?
- Pituitary - mild to mod depression of cortisol
Adrenal - does NOT suppress - 40% fail to suppress
- Urine / plasma catecholamine (normetanephrine)
Urine creatinine to normetanephrine ratio (most specific)
Serum inhibit assay (low or undetectable with pheo)