Lecture 20: Endocrine 2 Flashcards
What are the relevant anatomical structures near the adrenal glands
They are located at the cranial pole of the kidney
near the
- Ca. VC
- aorta
- the phrenicoabdominal vein runs right over top (landmark)
What are the parts of the adrenal gland and what do they secrete?
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
What is the functions of cortisol
spare glucose
- lipolysis
- gluconeogenesis
- protein catabolism
causes reduced:
- wound healing
- inflammation
- immunity
What are the 3 main disorders of the adrenal cortex
hypoadrenocorticism
hyperadrenocorticism
adrenal neoplasia
What is the common signalment of an animal with hypoadrenocorticism?
idiopathic adrenocortical atrophy
- young adult dog
- all breeds, esp (poodle/great dane/nova scotia duck tolling retriever)
What is the pathogenesis of hypoadrenocorticism
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
What are the clinical signs of hypoadrenocorticism
v/d/lethargy/shock
cardiovascular collapse = addisonian crisis
- hypovolemic shock
- sudden death
What are the gross lesions of hypoadrenocorticism? What is the mechanism of dysfunction?
small adrenal glands
primary hypofunction
(but for atypical addison’s it is caused by iatrogenic or secondary hypofunction)
What is the common signalment for hyperadrenocorticism?
dogs (uncommon in cats)
most common canine endocrinopathy
What are the 3 main mechanisms of dysfunction of hyperadrenocorticism? What gross lesions does each mechanism cause?
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
What are the clinical signs of hyperadrenocorticism?
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
What is the typical signalment of an animal presenting with adrenal neoplasia? How does signalment differ depending on neoplasia type?
old dogs: adenoma > carcinoma
ferrets:
- female > male
- had early gonadectomy
- spectrum of lesions
uni or bilateral hyperplasia or carcinoma > adenoma
Compare adenoma and carcinomas of adrenal neoplasias causing hyperadrenocorticism
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
What is the pathogenesis of adrenal neoplasia in ferrets
early gonadectomy can increase the risk
- removal will impair feedback mechanisms
- increase GnRH
- increased LH/FSH
- target reticularis
- increased estradiol 17B but normal cortisol
What are the clinical signs of adrenal neoplasia in ferrets
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
What is the main dysfunction of the adrenal medulla
pheochromocytoma
- benign or malignant
- come functional causing increased catecholamine/hypertension
What species are pheochromocytomas common in?
dog and bulls
What is a common concurrent dysfunction with pheochromocytoma
C tell tumors of the thyroid
What are the relevant structures near the thyroid?
near
larynx
trachea
thymus
parotid salivary gland
What is the thyroid gland made up of
thyroid follicular cells
C/parafollicular cells
What is the function of thyroid follicular cells
makes T3/4
thyroglobin > monoiodotyrosine > diiodotyrosine > T3/T4
T3/4 has negative feedback on hypothalamus and anterior pit (TRH/TSH)
control metabolism and growth
What is the function of C cells?
release calcitonin in response to hypercalcemia
- cause deposition of calcium in bone
What is the common signalment of an animal with hypothyroidism
dog
- doberman
- daschund
What are the causes of hypothyroidism
primary thyroid disease
- idiopathic follicular collapse
- lymphocytic thyroiditis (lymphocytic infiltration and inflammation destry the thyroid = autoimmune)
secondary disease = rare
- hypothalamic or pituitary lesion
What are the clinical signs of hypothyroidism?
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
What are 2 types of congenital hypothyroidism
goiter
congenital hypothyroidism dysmaturity syndrome (CHDS)
What is goiter
non neoplastic/non inflammatory enlargement of the thyroid
thyroid follicular hyperplasia
- due reduced T3/4 synthesis and increased TSH/TRH stimulation
What are the causes of goiter
iodine deficiency
goiterogenic agents (make iodine less available)
excessive iodine diets (inhibit follicular cell function)
genetic enzyme defects
- dyshormonogenic goiter
What are the clinical signs and gross signs of goiter
cervical tracheal mass
alopecia
myedema
common cause for abortion in small ruminants
bilateral enlarged dark purple thyroids
What are the clinical signs of congenital hypothyroidism dysmaturity syndrome?
perinantal death (soon after birth)
MSK abnormalities
- mandible prognathia
-ruptured tendons
- immature carpal and tarsal bones
- look immature
- sine/silky hair
prolonged gestaion
What are the gross signs of CHDS? How to diagnose?
thyroid grossly normal
- NEED histo
check jaw and limb radiographs
- see the immature carpal and tarsals
What is the cause of CHDS?
unknown
What are 4 causes of thyroid hyeprfunction?
hyperthyroidism
nodular hyperplasia
thyroid follicular tumor
thyroid follicular carcinoma
What lesions cause hyperthyroidism and what mechanism of dysfunction is it?
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
How does the clinical effects of hyperthyroidism differ if it is caused by an adenoma vs a carcinoma?
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
What animals are most commonly affected by thyroid nodular hyperplasia
old cats
- usually functional
dog/horse
- usually non-functional/incidental
What are the gross lesions associated with nodular hyperplasia
multiple tan/brown encapsulated nodules
What species is benign thyroid follicular tumors common in?
cats
What are the gross features of benign thyroid follicular tumors
single
white/tan encapsulated nodules
What species is thyroid follicular carcinomas most common in
dogs
What are the gross and clinical signs of thyroid follicular carcinoma?
can be found in ectopic thyroid tissue
invasive - metastasize to the lungs
clinically:
- dyspnea
- voice change
What is the main C/parafollicular disorder?
C/parafollicular cell tumors
- adenoma or carcinoma
What species do C cell tumors affect the most?
old bulls
What causes C cell tumors
may have dietary influences
- high calcium (dairy cow) diets fed to beef cows
What disease is often concurrent with C cell tumors
pheochromocytoma or pituitary tumors
