Endocrine 3 Flashcards
What are some clinical signs of hypothyroidism?
-Reduced basal metabolic rate (weight gain)
-bilaterally symmetrical alopecia
-hyperkeratosis
-hyperpigmentation
-myxedema
-hypercholesterolemia leading to atherosclerosis
What are two examples of congenital hypothyroid disorders?
Goiters, CHDS in foals
What is a goiter?
A non-specific term used to describe a non-neoplastic, non-inflammatory enlargement of the thyroid glands
What are four causes of goiters?
Iodine deficient diets, goitrogenic compounds, excess dietary iodine, genetic enzyme defects (dyshormonogenetic goiter)
What is the pathogenesis of a goiter?
Inadequate thyroid hormone synthesis → decreased blood levels of T3 and T4 → increased TRH → increased TSH → hypertrophy/hyperplasia of follicular cells
What is congenital hypothyroidism-dysmaturity syndrome (CHDS) in foals?
A condition in foals causing perinatal death and MSK malformations (have a prolonged gestation but appear to be born premature)
How can you diagnose CHDS in foals?
Grossly the thyroid may look normal, but microscopic lesions are present. If you are suspicious based on the clinical signs, make sure to ALWAYS TAKE THYROID FOR HISTOLOGY!
What are the two most common endocrine diseases of cats?
Hyperthyroidism, diabetes mellitus
What mechanism of endocrine disease is hyperthyroidism?
Primary hyperfunction (#2)
Why is hyperthyroidism less common in dogs?
Dogs are very good at excreting excess iodine versus cats are bad at conjugating excess thyroid hormone and iodine
What are the clinical signs of hyperthyroidism?
Increased basal metabolic rate (cachexia), hyperexcitable and heat intolerant, tachycardia and dysrhythmias, PUPD, concentric hypertrophy of the heart (do not get this confused with HCM - heart lesions due to hyperthyroidism are reversible)
What are three proliferative thyroid lesions that cause hyperthyroidism?
Thyroid follicular adenoma, thyroid follicular carcinoma, multifocal nodular hyperplasia
When dogs develop a thyroid lesion, is it more likely to be benign or malignant? What is this neoplasia called?
Malignant (thyroid follicular carcinoma)
When cats develop a thyroid lesion, is it more likely to be benign or malignant? What is this neoplasia called?
Benign (thyroid follicular adenoma)
What does multifocal nodular hyperplasia look like grossly?
Multiple tan to brown non-encapsulated nodules
Can’t differentiate from follicular cell adenoma grossly
Multifocal nodular hyperplasia is most common in which species?
Cats (functional/active in cats versus inactive in other species)
Thyroid follicular cell adenomas are most common in which species?
Cats
What do thyroid follicular cell adenomas look like grossly?
Single, white to tan, well-defined, and encapsulated
Can’t differentiate from multifocal nodular hyperplasia grossly
Thyroid follicular cell carcinomas are most common in which species?
Dogs (invasive and early metastasis to the lungs)
What do thyroid C-cells secrete? What is the function of this hormone?
Calcitonin. To decrease blood calcium levels (stimulated by high blood calcium levels)
What are thyroid C-cell tumors?
Neoplasias derived from C cells (parafollicular cells) of the thyroid gland
What is the cause of thyroid C-cell tumors?
Cause is unknown but likely related to high calcium diets
Which species do thyroid C-cell tumors occur most commonly in?
Old bulls (they get fed the same thing as dairy cows sometimes but the difference is that the bulls don’t have the reservoir for calcium because they aren’t lactating)
True or False: Thyroid C-cell tumors can be both benign and malignant
True
What is the function of the parathyroid gland?
It regulates blood calcium and phosphorus levels
Which hormone does the parathyroid gland secrete? What is the function of this hormone?
Parathyroid hormone (PTH) by chief cells. PTH stimulates the release of calcium in an indirect process through osteoclasts
What is primary hyperparathyroidism?
Hyperparathyroidism due to functional parathyroid tumors
What is secondary hyperparathyroidism?
Hyperparathyroidism due to renal and nutritional issues
What is pseudohyperparathyroidism also known as?
Hypercalcemia of malignancy
What is the mechanism behind hypercalcemia of malignancy?
Hypercalcemia of malignancy is primarily caused by the secretion of parathyroid hormone-related protein (PTHrP) by cancer cells. PTHrP mimics the action of parathyroid hormone (PTH) and acts on the same receptors in the bone and kidney.
What mechanism of endocrine disease is nutritional secondary hyperparathyroidism?
Hyperactivity caused by diseases in other organs (#5)
What are four potential causes of hypoparathyroidism?
Lymphocytic parathyroiditis, destruction by a primary or metastatic tumor, parathyroid gland atrophy, accidental surgical removal
Primary hyperparathyroidism is the result of a functional neoplasm of which cell?
Chief cell
What are two consequences of excess parathyroid hormone?
- Bone lesions from widespread osteoclastic resorption (ex. fibrous osteodystrophy)
- Hypercalcemia
Remember PTH is basically stealing from Peter to pay Paul - it’s going to take calcium from bones to put into blood which can lead to severe bone consequences
Which is more common with primary hyperthyroidism, adenomas or carcinomas?
Adenomas
What is a nutritional cause of secondary hyperparathyroidism?
A high phosphorus diet or a low calcium diet (remember, calcium and phosphorus should be in a proper ratio)
What will the parathyroid glands look like grossly with nutritional or renal secondary hyperparathyroidism?
Enlargement of all parathyroid glands
What will the parathyroid glands look like grossly with hypercalcemia of malignancy?
Atrophied
What mechanism of endocrine disease is hypercalcemia of malignancy?
Hypersecretion of hormonal factors from a non-endocrine source (#3)
What is the most common cause of hypercalcemia?
Hypercalcemia of malignancy
Which cells of the pancreas secrete insulin?
β cells
What are the three categories of disorders of the endocrine pancreas? Name an example of each.
- Insulin dysregulation (equine metabolic syndrome)
- Hypofunction of islet cells (diabetes mellitus)
- Hyperfunction of islet cells (insulinomas)
What is equine metabolic syndrome (EMS)?
A disorder of insulin dysregulation seen in horses (inability to regulate blood insulin)
What is the most important complication of EMS?
Endocrinopathic laminitis
Which horses are more at risk for EMS?
Physically inactive horses consuming high-energy rations (lots of grass), certain breeds (ponies, donkeys, mustangs, etc.)
What is the most common clinical sign of EMS?
Regional adiposity (‘cresty’ neck)
Which disease can horses have concurrently with EMS?
PPID
What are the two categories of insulin deficiency?
- Absolute or Type 1
- Relative or Type 2
What is type 1 insulin deficiency?
The inadequate synthesis and release of insulin from β cells due to the autoimmune destruction of β cells
What is type 2 insulin deficiency?
The failure of target cells to respond to insulin
Cats commonly get type ______ diabetes mellitus
2
Dogs commonly get type ______ diabetes mellitus
1
What is the mechanism of endocrine disease for each type of diabetes mellitus?
Type 1: Primary hypofunction (#1)
Type 2: Failure of target cells to respond (#4)
What is the principal extrapancreatic finding of diabetes mellitus on necropsy?
Hepatic lipidosis
Diagnosis of diabetes mellitus is best seen clinically versus on necropsy
True. Gross pancreatic lesions are often absent and extrapancreatic lesions may be present
What is the most common β cell neoplasm?
Insulinomas
Which animals most commonly get insulinomas?
Ferrets
Insulinomas in ferrets are usually _________ whereas insulinomas in dogs are usually __________
Benign in ferrets, malignant in dogs
What are the two main chemoreceptor organs?
- Aortic body (base of the heart)
- Carotid body (bifurcation of the common carotid artery)
What are neoplasms of the chemoreceptor organs called?
Chemodectomas
Do chemodectomas occur more frequently at the aortic body or carotid body?
Aortic body
Chemodectomas that arise from the aortic body are more likely ___________ and chemodectomas that arise from the carotid body are more likely ________
Adenomas, carcinomas
Chemodectomas are more common in which breeds of dog?
Brachycephalic breeds
True or False: Chemodectomas are functional
False. They are non-functional but they are space occupying
