Endocrine Flashcards
What enzyme converts pyruvate to lactate?
Lactate Dehydrogenase
List the 7 stimuli for PTH secretion
Hypocalcemia, epinephrine, isoproterenol, dopamine, secretin, prostaglandin E2, and stimulation of nerve endings in the parathyroid gland
What inhibits PTH secretion?
High serum and intercellular iCa via increased arachidonic acid and possibly subsequent eicosanoid production. Calcitriol also inhibits PTH mRNA synthesis
What is the principal stimulus for PTH secretion?
Hypocalcemia
What are the clinical hallmarks of myxedema coma in human beings?
Altered mental status, inadequate thermoregulation, decreased respiratory and cardiac function, concurrent disease
T/F- Coma is commonly seen with myxedema coma?
False- it is rarely seen; more commonly disorientation, confusion, lethargy
What are the proposed mechanisms of altered mental status in myxedema coma?
Decreased blood flow and O2 delivery to the brain, hyponatremia, lack of direct effect of thyroid hormone on the brain, disruption of integrity of the BBB
What are the proposed mechanisms of altered thermoregulation in myxedema coma?
inadequate thyroid hormone function in the hypothalamus, decrease in calorigenic effect of thyroid hormones, hypoperfusion and hypotension
List things that contribute to hypoventilation in myxedema coma?
Decreased respiratory system responsiveness to hypoxia and hypercapnia, obesity, muscle weakness, pneumonia, pericardial or pleural effusion, ascites
Why does systolic hypotension occur commonly in people with myxedema coma?
secondary to bradycardia, decreased cardiac output, hypovolemia
Why might diastolic hypertension occur with myxedema coma?
peripheral vasoconstriction and central shunting of blood secondary to hypothermia and low O2 consumption
List mechanisms of edema formation with myxedema coma
accumulation of the glycosaminoglycan hyaluronic acid in the dermis, impaired renal perfusion due to decreased cardiac output, excessive secretion of ADH causing hyponatremia/fluid retention/edema
Proposed risk factors in dogs for development of myxedema coma?
- Rottweiler dogs, middle age, untreated hypothyroidism, concurrent disorder (most commonly infection)
- POSSIBLY steroid or NSAID administration
- Risk factors in people- recent surgery, burns, CO2 retention, hypothermia, infection, hypoglycemia, GI hemorrhage, stroke, trauma, medications
T/F- female dogs are at an increased risk for developing myxedema coma?
False, although in people females are at an increased risk
Name some clinical signs associated with chronic untreated hypothyroidism
weight gain, obesity, lethargy, mental dullness, weakness, hyperkeratosis, alopecia, thin hair coat
What are the most common clinicopathologic abnormalities in hypothyroid dogs? What additional abnormalities are found in people but not necessarily dogs?
- mild nonregenerative anemia, hypercholesterolemia, lipemia, increased ALP
- people: hyponatremia, hypoglycemia
What is a pheochromocytoma?
Tumor of the chromaffin cells of the adrenal medulla
What do the chromaffin cells of the adrenal medulla do?
They synthesize, store, and secrete catecholamines in response to sympathetic stimulation.
They are also termed APUD cells as they are responsible for amine precursor uptake and decarboxylation
In humans, most pheochromocytomas secrete what catecholamine?
Norepinephrine
What percentage of dogs with a pheochromocytoma are symptomatic?
30-50% have clinical signs attributable to the tumor
What are common clinical signs seen with a pheochromocytoma?
Hypertension Weakness Collapse Lethargy Vomiting Diarrhea PU/PD Tachypnea Abdominal distension Syncope Tachyarrhythmias Bradyarrhthymias Abdominal pain