Endocrine

Question 2

Describe 3 zones of adrenal gland and what they produce

Answer 2

Outer: zona glomerulosa (salt) - mineralocorticoids = aldosterone
Middle: zona fasciculata (sugar) - glucocorticoids
Inner: zona reticularis (sex + steroids) - androgens, estrogens, epinephrine / norepinephrine (from Chromatin cells)

Question 3

What are effects of norepinephrine on alpha / beta receptors?

Answer 3

alpha - cause vasoconstriction through increased resistance - increase SAP
beta 1 - increase force contraction & increase HR

Question 4

Describe arterial and venous supply to thyroid glands & innervation

Answer 4

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.)

Question 5

What are the arterial / venous supply of adrenal glands?

Answer 5

Phrenicoabdominal a, renal a, cranial abdominal a

R adrenal v –> caudal vena cava

L adrenal vein –> Left renal vein

Question 6

Location of external / internal parathyroids?
Vascular and nerve supply?

Answer 6

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.

Question 7

Describe pathway of RAAS and how it creates aldosterone

Answer 7

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

Question 8

Where is PTH made, by what cell, and describe its effects to adjust Ca/P
Where is calcitonin made and what does it do?

Answer 8

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

Question 9

Where is ectopic thyroid or parathyroid tissue found?

Answer 9

TH: trachea, thoracic inlet, mediastinum, descending aorta (thorax)
PTH: 3-6% of dogs - thymus; detected histologically in 35-50% of cats

Question 10

Describe the effects of epinephrine on the various receptors

Answer 10

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)

Question 11

Describe pathway to make thyroid hormone & which are biologically active

Answer 11

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

Question 12

How are catecholamines formed?
Rate of Norepi/epi in cats vs dogs?
Where are the alpha 1, alpha 2, beta 1, beta 2 receptors?

Answer 12

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

Question 13

Name the (+) and (-) functions of glucocorticoids

Answer 13

+ 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

Question 14

1. What size usually says adrenal is “too large”?
2. What are guidelines for malignancy on CT vs US?
3. What is accuracy of CT to ID vascular invasion?
4. What % of Cushing’s have pituitary form?

Answer 14

1. 1.5 cm or greater
2. Mass size (>20 mm); invasion of mass into surrounding tissues and BVs; identification of additional mass lesions
3. 95% accurate
4. 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)

Question 15

1. Between pituitary dependent & adrenal dependent Cushing’s, which shows suppression of cortisol with LDDST?
2. What % of pituitary do / don’t suppress?
3. What are diagnostic tests to test for pheochromocytoma?

Answer 15

1. Pituitary - mild to mod depression of cortisol
   Adrenal - does NOT suppress
2. 40% fail to suppress
3. Urine / plasma catecholamine (normetanephrine)
   Urine creatinine to normetanephrine ratio (most specific)
   Serum inhibit assay (low or undetectable with pheo)

Question 16

1. What are the 3 qualifiers of suppression on LDDST?
2. Dogs with iatrogenic Cushing’s have __ ACTH and __ cortisol
3. To prep for adrenal cortisol secreting tumor - dose trilostane and goal therapy cortisol?
4. If increase blood pressure, what drug to give with cortisol tumor and why?

Answer 16

1. • 4 hr post serum cortisol [ ] <1.5 ug/dL
     - 4 hr post cortisol [ ] <50% baseline [ ]
     - 8 hr post cortisol [ ] <50% baseline [ ]
2. Low ACTH; subnormal baseline cortisol
3. 1-2 mg/k PO q12 ; cortisol 2-5 ug/dL
4. ACE inhibitor - decreases peripheral vasoconstriction and aldosterone secretion

Question 17

With adrenal surgery, what is protocol of glucocorticoids to decrease risk of Addison’s?

Answer 17

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

Question 18

1. When should you treat with mineralocorticoids and what is the treatment?
2. What is pre-tx before surgery for Pheochromocytomas and dose?
3. If has increased BP and tachycardia with Pheos, what is the treatment and give when?

Answer 18

1. Na <135 mEq/L or if K > 6.5 mEq/L
   - desoxycorticoosterone pivalate
2. ideally phenoxybenzamine 2-3 weeks before 0.5 mg/kg PO q12 OR prazosin 0.5-1 mg/kg q8h (depend size pt)
3. Propanolol or atenolol (beta adrenergic antagonist) ONLY AFTER alpha adrenergic blockade (via phenoxy)!!!!

Question 19

1. What % malignant thyroid tumor in dogs metastasize?
2. What % malignant thyroid tumor in dogs are hyperthyroid?
3. What breed of dogs are predisposed to thyroid tumors?
4. What % specificity does CT have for ID invasion of tumor?
5. What are benefits of scintigraphy for thyroid tumors in dogs?

Answer 19

1. 40% detectable at presentation
2. 10-29%
3. Golden Rets, Beagles, Siberian Husky
4. 100%
5. Helps ID ectopic tissue; I131 treatment - can determine likelihood of response

Question 20

1. What is treatment of hypothyroidism post-op thyroidectomy? Dose?
2. MST of treatment with surgery vs untreated thyroid carcinoma?
3. What are factors positively associated with local invasiveness?
4. List 3 metastatic rates based on 3 volume sizes of tumors

Answer 20

1. Levothyroxine 0.02 mg/kg POq12; max dose 0.8 mg POq12
2. MST ~22-28 months with surgery (newer studies); w/o surgery 3 months
3. Tumor diameter, tumor volume, tumor fixation, ectopic location, follicular cell origin
4. 14% tumors <23 cm^3
   74% tumors 23-100 cm^3
   100% tumors >100 cm^3

Question 21

1. List options to ID abnormal parathyroid gland intra-op
2. What is dose of calcitriol to treat hypoCa post parathyroidectomy?
3. What is the goal Ca range with treatment?
4. What breed is predisposed for hyperparathyroidism
5. What are two other treatment options for PTH tumors? MST? What is percentage of controlled hyperCa?

Answer 21

1. Rapid chemiluminescent assay;
   methylene blue IV;
   indocyanine green near infrared fluorescent imaging
2. 0.02-0.03 ug/kg/d POq12 2-4 days then 0.005-0.015 ug/kg/d
3. Total 8-9.5 - iCa 0.9-1.2 mmol/L
4. Keeshond
5. Percutaneous ethanol (72%) MST 540 days
   Percutaneous heat ablation (90%) MST 581 days

Question 22

1. To diagnose PTE post-op adrenal surgery, what are dx tests? Gold standard?
2. Treatment for PTE?

Answer 22

1. clinical signs, BW
   Blood gas: Increase pAO2 - paO2 gradient on room air (but paO2/paCO2 normal)
   Rads: interstitial infiltrates
   Pulmonary angiography - gold standard
2. Anticoagulant
   Sildenafil
   Theophylline
   +/- mechanical vent?

Question 23

1. Advantage of flank vs midline vs laparoscopic adrenalectomy?
2. What % of caval invasion in adrenocortical vs pheochromocytomas
3. What is current mortality rates for adrenalectomy?
4. MST for not having surgery for adrenal tumors?

Answer 23

1. Midline: easier access to CdVC
   Flank: improve exposure dorsal abdomen
   Laparoscopy: small incisions - improved visualization and exposure
2. Adrenocortical 11-16%
   Pheochromocytomas 35-55%
3. 4-22% mortality
4. MST 15-17 months with medical mgmt

Question 24

1. With cat adrenal tumors, what % are cortical? Functional?
2. Survival rate for cats - 77% for at least two weeks, but what is MST?
3. What are other conditions occur with ferrets with adrenal tumors?
4. Mortality rate post-adrenalectomy for ferrets?

Answer 24

1. 91% cortical; 76% functional
2. 50 weeks
3. Splenomegaly (87%)
   Insulinoma (27%)
   Cardiomyopathy (10%)
4. <2% mortality

Question 25

1. Between dogs/cats with thyroid nodules on PE, what % are malignant? 2. For cat thyroid tumors, what % are bilateral? 3. What is best approach to evaluate renal disease w thyroid cats? 4. What % hyperTH cats had chronic renal disease? 5. What % hyperTH cats had hypokalemia; what is the clinical sign?

Answer 25

1. Cats <1-4% malignant; Dogs >90% 2. 70-91% bilateral 3. Trial course with methimazole and effects reversible when discontinued (monitor chem with tx) 4. 40% had CRD 5. 32% hypoK - neck ventroflexion

Question 26

1. What % cats with hyperTH have palpable nodule? 2. Tx options to make euthyroid pre-op for cats? 3. What condition is it not recommended to do sx for feline hyperthyroid? 4. List sx approaches to removal thyroid gland 5. With parathyroid autotransplantation, what is timeline it starts to function?

Answer 26

1. >90% 2. Propylthiouracil and methimazole (1.25-2.5 mg BID) 3. If azotemia with euthyroid state -> surgery not OK, do methimazole 4. Modified extracapsular Modified intracapsular Intracapsular Extracapsular - also can do staged 5. 7-21 days

Question 27

1. Prognosis thyroidectomy cats 2. Complications of thyroidectomy in cats 3. What % cats get significant hypoCa post-op? 4. List tx options and doses for hypoCa post-op

Answer 27

1. Excellent - low mortality rate 2. Hemorrhage Lar par Dyspnea Horner's HypoTH HypoPTH Recurrent hypoTH 3. <6% 4. 10% Ca gluconate IV 0.25-1.5 mL/kg slowly (over 10-20 min) to effect or CRI at 5-15 mg/kg/h IV. Ca lactate or carbonate 0.5-1 g of calcium/cat/d orally. Oral vitamin D can be in the form of either dihydrotachysterol or calcitriol Calcitriol 0.02 to 0.03 µg/kg/d for 2 to 4 days then 0.005 to 0.015 µg/kg/d Dihydrotachysterol 0.03 mg/kg once daily for 1 to 7 days, then 0.02 mg/kg/d

Question 28

1. What % cats recur with hyperTH? 2. What is prognosis for I131 for hyperTH? 3. Of all thyroid tumors in dogs, what % benign? Of those felt on PE, what % benign? 4. What % canine malignant tumors are bilateral? 5. Where are ectopic thyroid noted in dog?

Answer 28

1. 5-11% recur 2. Single dose cures most 3. ~30-50% adenoma; <10% malignant 4. 25-47% bilateral 5. Base of tongue, cranial mediastinum, ventral neck, heart base

Question 29

1. Canine thyroid tumors - I131 MST? (W vs W/O mets?) 2. Canine thyroid tumors - RT MST? 3. With partial hyoidectomy for sublingual ectopic thyroid tumors - what should you protect? 4. What are primary, secondary, tertiary hypothyroidism dogs?

Answer 29

1. W/O 839 days; W mets 366 days 2. Mean progression free survival 45 months; 3 year PFS 75%; others ~24 months 3. Hypoglossal and recurrent laryngeal n 4. Primary: disease of thyroid gland Secondary: problem with pituitary gland Tertiary: hypothalamus unable to produce enough TRH

Question 30

1. For the list of diseases, say if PTH, PTHrp, iCa, and vitamin D? ⬆️⬇️ Primary hyperPTH LSA CRF AGASACA Hypervitaminosis D

Answer 30

Primary hyperPTH: PTH ⬆️; PTHrp ⬇️; iCa ⬆️; Vit D ⬆️ LSA: PTH ⬇️; PTHrp ⬆️; iCa ⬆️; Vit D ⬇️ CRF: PTH ⬆️; PTHrp ⬆️; iCa ⬇️; Vit D ⬇️ AGASACA: PTH ⬇️; PTHrp ⬆️; iCa ⬆️; Vit D ⬆️ HyperVit D: PTH ⬇️; PTHrp ⬇️; iCa ⬆️ Vit D ⬆️