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)
- What are the 3 qualifiers of suppression on LDDST?
- Dogs with iatrogenic Cushing’s have __ ACTH and __ cortisol
- To prep for adrenal cortisol secreting tumor - dose trilostane and goal therapy cortisol?
- If increase blood pressure, what drug to give with cortisol tumor and why?
- 4 hr post serum cortisol [ ] <1.5 ug/dL
- 4 hr post cortisol [ ] <50% baseline [ ]
- 8 hr post cortisol [ ] <50% baseline [ ]
- 4 hr post serum cortisol [ ] <1.5 ug/dL
- Low ACTH; subnormal baseline cortisol
- 1-2 mg/k PO q12 ; cortisol 2-5 ug/dL
- ACE inhibitor - decreases peripheral vasoconstriction and aldosterone secretion
With adrenal surgery, what is protocol of glucocorticoids to decrease risk of Addison’s?
Post-op dexamethasone (0.05-0.1 mg/kg) in IVF over 6 hours OR
ACTH stim immediately post-op and before exogenous steroids to get baseline
- if Addisonian - taper dose (decrease dose by 0.02 mg/kg/q24h) dexamethasone at 12 hour intervals until dog is given orals (24-72 h post-op)
- oral pred 0.25-0.5 mg/kg q12 tapered to 0.1 mg/kg/d by 10d
ALWAYS at 4 week - check ACTH stim before stopping GCs
- When should you treat with mineralocorticoids and what is the treatment?
- What is pre-tx before surgery for Pheochromocytomas and dose?
- If has increased BP and tachycardia with Pheos, what is the treatment and give when?
- Na <135 mEq/L or if K > 6.5 mEq/L
- desoxycorticoosterone pivalate - ideally phenoxybenzamine 2-3 weeks before 0.5 mg/kg PO q12 OR prazosin 0.5-1 mg/kg q8h (depend size pt)
- Propanolol or atenolol (beta adrenergic antagonist) ONLY AFTER alpha adrenergic blockade (via phenoxy)!!!!
- What % malignant thyroid tumor in dogs metastasize?
- What % malignant thyroid tumor in dogs are hyperthyroid?
- What breed of dogs are predisposed to thyroid tumors?
- What % specificity does CT have for ID invasion of tumor?
- What are benefits of scintigraphy for thyroid tumors in dogs?
- 40% detectable at presentation
- 10-29%
- Golden Rets, Beagles, Siberian Husky
- 100%
- Helps ID ectopic tissue; I131 treatment - can determine likelihood of response
- What is treatment of hypothyroidism post-op thyroidectomy? Dose?
- MST of treatment with surgery vs untreated thyroid carcinoma?
- What are factors positively associated with local invasiveness?
- List 3 metastatic rates based on 3 volume sizes of tumors
- Levothyroxine 0.02 mg/kg POq12; max dose 0.8 mg POq12
- MST ~22-28 months with surgery (newer studies); w/o surgery 3 months
- Tumor diameter, tumor volume, tumor fixation, ectopic location, follicular cell origin
- 14% tumors <23 cm^3
74% tumors 23-100 cm^3
100% tumors >100 cm^3
- List options to ID abnormal parathyroid gland intra-op
- What is dose of calcitriol to treat hypoCa post parathyroidectomy?
- What is the goal Ca range with treatment?
- What breed is predisposed for hyperparathyroidism
- What are two other treatment options for PTH tumors? MST? What is percentage of controlled hyperCa?
- Rapid chemiluminescent assay;
methylene blue IV;
indocyanine green near infrared fluorescent imaging - 0.02-0.03 ug/kg/d POq12 2-4 days then 0.005-0.015 ug/kg/d
- Total 8-9.5 - iCa 0.9-1.2 mmol/L
- Keeshond
- Percutaneous ethanol (72%) MST 540 days
Percutaneous heat ablation (90%) MST 581 days
- To diagnose PTE post-op adrenal surgery, what are dx tests? Gold standard?
- Treatment for PTE?
- clinical signs, BW
Blood gas: Increase pAO2 - paO2 gradient on room air (but paO2/paCO2 normal)
Rads: interstitial infiltrates
Pulmonary angiography - gold standard - Anticoagulant
Sildenafil
Theophylline
+/- mechanical vent?
- Advantage of flank vs midline vs laparoscopic adrenalectomy?
- What % of caval invasion in adrenocortical vs pheochromocytomas
- What is current mortality rates for adrenalectomy?
- MST for not having surgery for adrenal tumors?
- Midline: easier access to CdVC
Flank: improve exposure dorsal abdomen
Laparoscopy: small incisions - improved visualization and exposure - Adrenocortical 11-16%
Pheochromocytomas 35-55% - 4-22% mortality
- MST 15-17 months with medical mgmt
- With cat adrenal tumors, what % are cortical? Functional?
- Survival rate for cats - 77% for at least two weeks, but what is MST?
- What are other conditions occur with ferrets with adrenal tumors?
- Mortality rate post-adrenalectomy for ferrets?
- 91% cortical; 76% functional
- 50 weeks
- Splenomegaly (87%)
Insulinoma (27%)
Cardiomyopathy (10%) - <2% mortality
