Lecture 20: Endocrine 2

Question 1

What are the relevant anatomical structures near the adrenal glands

Answer 1

They are located at the cranial pole of the kidney

near the
- Ca. VC
- aorta
- the phrenicoabdominal vein runs right over top (landmark)

Question 2

What are the parts of the adrenal gland and what do they secrete?

Answer 2

Cortex
zona glomerulosa
- mineralocorticoids: aldosterone (under control of RAAS, act on distal tubule = excrete K and resorb Na)

zona fasciculata
- glucocorticoids: cortisol release under ACTH control

zona reticularis
- androgens/progesterone/estrogen: under ACTH control

Medulla: catecholamines

cortex : medulla : cortex ratio
1 : 2 : 1

Question 3

What is the functions of cortisol

Answer 3

spare glucose
- lipolysis
- gluconeogenesis
- protein catabolism

causes reduced:
- wound healing
- inflammation
- immunity

Question 4

What are the 3 main disorders of the adrenal cortex

Answer 4

hypoadrenocorticism
hyperadrenocorticism
adrenal neoplasia

Question 5

What is the common signalment of an animal with hypoadrenocorticism?

Answer 5

idiopathic adrenocortical atrophy
- young adult dog
- all breeds, esp (poodle/great dane/nova scotia duck tolling retriever)

Question 6

What is the pathogenesis of hypoadrenocorticism

Answer 6

can affect all layers

mineralocorticoids = hyperkalemia/hyponatremia and hypochloremia = hypovolemia

glucocorticoids = GI signs/hypoglycemia/low cortisol
- no response to ACTH stimulation

reduced sex hormones

may be immune mediated

Question 7

What are the clinical signs of hypoadrenocorticism

Answer 7

v/d/lethargy/shock

cardiovascular collapse = addisonian crisis
- hypovolemic shock
- sudden death

Question 8

What are the gross lesions of hypoadrenocorticism? What is the mechanism of dysfunction?

Answer 8

small adrenal glands

primary hypofunction
(but for atypical addison’s it is caused by iatrogenic or secondary hypofunction)

Question 9

What is the common signalment for hyperadrenocorticism?

Answer 9

dogs (uncommon in cats)

most common canine endocrinopathy

Question 10

What are the 3 main mechanisms of dysfunction of hyperadrenocorticism? What gross lesions does each mechanism cause?

Answer 10

functional corticotroph adenoma in the anterior pituitary
- secondary hyperfunction
- most common 85-90%
- bilateral adrenocortical hypertrophy/hyperplasia

functional adrenal neoplasia
- primary hyperfunction
- 10-15%
- unilateral neoplasia nodule and cortical atrophy in contralateral gland

iatrogenic
- bilateral adrenocortical atrophy

Question 11

What are the clinical signs of hyperadrenocorticism?

Answer 11

polyphagia

PU/PD
- cortisol impacts kidneys ability to recognize ADH

muscle weakness
- pot-bellied
- lordosis
- temor
- straight legged position

cutaneous lesions
- alopecia
- thin skin
- calcinosis cutis (dystrophic - no increase in blood P/Ca): causes foreign body reaction in skin = pruritus and ulceration

steroid hepatopathy + hepatomegaly
- vacuolated hepatocytes

increased secondary infection

reduced wound healing

Question 12

What is the typical signalment of an animal presenting with adrenal neoplasia? How does signalment differ depending on neoplasia type?

Answer 12

old dogs: adenoma > carcinoma

ferrets:
- female > male
- had early gonadectomy
- spectrum of lesions
uni or bilateral hyperplasia or carcinoma > adenoma

Question 13

Compare adenoma and carcinomas of adrenal neoplasias causing hyperadrenocorticism

Answer 13

adenoma: common in old dogs
- usually nonfunctional but can be functional

carcinomas: uncommon
- old dogs/cattle
- functional and invasive
- often metastasize to kedneys/liver/LN/lungs

Question 14

What is the pathogenesis of adrenal neoplasia in ferrets

Answer 14

early gonadectomy can increase the risk
- removal will impair feedback mechanisms
- increase GnRH
- increased LH/FSH
- target reticularis
- increased estradiol 17B but normal cortisol

Question 15

What are the clinical signs of adrenal neoplasia in ferrets

Answer 15

bilateral and symmetrical alopecia

enlarged vulva (female) or enlarged prostate resulting un urethral blockage (male)

pancytopenia
- estrogen is toxic to hematopoietic precursors in bone marrow

+/- concurrent insulinoma

Question 16

What is the main dysfunction of the adrenal medulla

Answer 16

pheochromocytoma
- benign or malignant
- come functional causing increased catecholamine/hypertension

Question 17

What species are pheochromocytomas common in?

Answer 17

dog and bulls

Question 18

What is a common concurrent dysfunction with pheochromocytoma

Answer 18

C tell tumors of the thyroid

Question 19

What are the relevant structures near the thyroid?

Answer 19

near
larynx
trachea
thymus
parotid salivary gland

Question 20

What is the thyroid gland made up of

Answer 20

thyroid follicular cells

C/parafollicular cells

Question 21

What is the function of thyroid follicular cells

Answer 21

makes T3/4

thyroglobin > monoiodotyrosine > diiodotyrosine > T3/T4

T3/4 has negative feedback on hypothalamus and anterior pit (TRH/TSH)

control metabolism and growth

Question 22

What is the function of C cells?

Answer 22

release calcitonin in response to hypercalcemia
- cause deposition of calcium in bone

Question 23

What is the common signalment of an animal with hypothyroidism

Answer 23

dog
- doberman
- daschund

Question 24

What are the causes of hypothyroidism

Answer 24

primary thyroid disease
- idiopathic follicular collapse
- lymphocytic thyroiditis (lymphocytic infiltration and inflammation destry the thyroid = autoimmune)

secondary disease = rare
- hypothalamic or pituitary lesion

Question 25

What are the clinical signs of hypothyroidism?

Answer 25

weight gain (reduced basal metabolic rate) cutaneous lesions - bilateral/symmetrical alopecia - hyperkeratosis - hyperpigmentation - myxedema (accumulation of hydrophilic mucus in SC which draws fluid in) repro hypercholesterolemia - atherosclerosis in coronary vessels of dogs

Question 26

What are 2 types of congenital hypothyroidism

Answer 26

goiter congenital hypothyroidism dysmaturity syndrome (CHDS)

Question 27

What is goiter

Answer 27

non neoplastic/non inflammatory enlargement of the thyroid thyroid follicular hyperplasia - due reduced T3/4 synthesis and increased TSH/TRH stimulation

Question 28

What are the causes of goiter

Answer 28

iodine deficiency goiterogenic agents (make iodine less available) excessive iodine diets (inhibit follicular cell function) genetic enzyme defects - dyshormonogenic goiter

Question 29

What are the clinical signs and gross signs of goiter

Answer 29

cervical tracheal mass alopecia myedema common cause for abortion in small ruminants bilateral enlarged dark purple thyroids

Question 30

What are the clinical signs of congenital hypothyroidism dysmaturity syndrome?

Answer 30

perinantal death (soon after birth) MSK abnormalities - mandible prognathia -ruptured tendons - immature carpal and tarsal bones - look immature - sine/silky hair prolonged gestaion

Question 31

What are the gross signs of CHDS? How to diagnose?

Answer 31

thyroid grossly normal - NEED histo check jaw and limb radiographs - see the immature carpal and tarsals

Question 32

What is the cause of CHDS?

Answer 32

unknown

Question 33

What are 4 causes of thyroid hyeprfunction?

Answer 33

hyperthyroidism nodular hyperplasia thyroid follicular tumor thyroid follicular carcinoma

Question 34

What lesions cause hyperthyroidism and what mechanism of dysfunction is it?

Answer 34

It is an excess of T3/4 via primary hyperfunction multifocal nodular hyperplasia and thyroid follicular adenoma >> thyroid follicular carcinoma rarely dogs can get thyroid follicular carcinoma either uni or bilateral

Question 35

How does the clinical effects of hyperthyroidism differ if it is caused by an adenoma vs a carcinoma?

Answer 35

carcinoma - malignant and bad - rarely develop the clinical syndrome tho because dogs have more efficient enterohepatic excretion of thyroid hormones adenoma or hyperplasia - weight loss - polyphagia - Pu/PD (due to increased blood flow to kidney = excess ultrafiltrate) - nervous - heat intolerance - cardiac (tachycardia/arrhythmia/concentric hypertrophy) the hypertrophy is NOT a primary cardiomyopathy

Question 36

What animals are most commonly affected by thyroid nodular hyperplasia

Answer 36

old cats - usually functional dog/horse - usually non-functional/incidental

Question 37

What are the gross lesions associated with nodular hyperplasia

Answer 37

multiple tan/brown encapsulated nodules

Question 38

What species is benign thyroid follicular tumors common in?

Answer 38

cats

Question 39

What are the gross features of benign thyroid follicular tumors

Answer 39

single white/tan encapsulated nodules

Question 40

What species is thyroid follicular carcinomas most common in

Answer 40

dogs

Question 41

What are the gross and clinical signs of thyroid follicular carcinoma?

Answer 41

can be found in ectopic thyroid tissue invasive - metastasize to the lungs clinically: - dyspnea - voice change

Question 42

What is the main C/parafollicular disorder?

Answer 42

C/parafollicular cell tumors - adenoma or carcinoma

Question 43

What species do C cell tumors affect the most?

Answer 43

old bulls

Question 44

What causes C cell tumors

Answer 44

may have dietary influences - high calcium (dairy cow) diets fed to beef cows

Question 45

What disease is often concurrent with C cell tumors

Answer 45

pheochromocytoma or pituitary tumors