Exam 2 (Endocrine) Flashcards
What are the peripheral effects of the thyroid function?
- Heat generation
- stimulates ATP formation in mitochondria
- influences flux of ions
- stimulates metabolic processes (basal metabolic rate, protein synthesis regulation of protein, fat & carb metabolism
Thyroid hormone regulates the metabolism of ___, ___, & ___.
protein, fat & carbs
The thyroid sympathetic fibers pass through what to get to the thyroid?
- Cardiac periaterial plexus &
- superior & inferior thyroid plexus
What are the 2 main blood supply sources for the thyroid?
- The superior thyroid artery ( branch of the external carotid)
- inferior thyroid artery ( branch of the subclavian artery)
Decreased T3 levels can be due to?
Hypothyroidism,
cirrhosis,
uremia &
malnutrition
Decreased T4 levels can be due to?
Hypothyroidism,
androgens,
salicylates,
sulphonamides
What are some anti-thyroid drugs?
- PTU (Propylthiouracil),
- methimazole,
- carbimazole (inhibit the action of peroxidase enzyme)
Why are glucocorticoids given in hyperthyroidism?
They inhibit conversion from T4 to T3 & decrease the release of thyroid hormone
How does radioactive iodine work?
Destroys the follicular cells
How is a temporary hypoparathyroidism treated?
- High dose calcium,
- calcitrol (Vitamin D)
What post-op lab can predict hypocalcemia?
Low PTH
What is myxedema & S/S?
- Severe form of hypothyroidism
- S/S: stupor, coma, hypotension, hyponatremia, hypoventilation, hypothermia
Where does a pheochromocytoma arise from?
Chromaffin cells of the adrenal medulla.
What is a paraganglioma?
An extra-adrenal pheochromocytoma
What is stored in the adrenal medulla?
- 80% epinephrine &
- 20% norepinephrine
Epi & Norepi derive from?
Tyrosine
Alpha-2 receptor stimulation leads to?
- Inhibits release of NE, vasoconstriction.
- Stimulates cognition
Stimulation of which receptor causes glycogenolysis & insulin secretion?
Beta-2
Stimulation of which receptor causes sodium reabsorption?
Alpha-1
A pheochromocytoma is also called what?
The 10% tumor
What are the symptoms of pheochromocytomas?
HA, diaphoresis, N/V, anxiety
What do we look at when testing for pheochromocytoma?
Plasma Metanephrines
What metabolites are elevated in a 24hr urine test in a Pt with a Pheo?
Metanephrine, normetanephrine & vanillylmandelic acid
When is phenoxybenzamine initiated?
1-3 weeks before resection
What is another drug besides phenoxybenzamine?
Doxazosin
What does a medication plan for a pheo look like?
- Start alpha-1 med and wait for adequate blockade until starting a beta antagonist.
- Starting beta antagonist too early may lead to HTN crisis & pulmonary edema
What is the best VA for pheochromocytoma, & why?
Isoflurane d/t it being the least cardiac depressant
What is generally avoided in a parturient with a pheochromocytoma?
Vaginal delivery as it can lead to HTN crisis
The parathyroid primarily consists of ____.
Chief cells
What effect does lithium have on the parathyroid?
- Increases PTH secretion &
- decreases cell sensitivity to calcium.
What effect does vitamin D have on the parathyroid?
Decreases PTH secretion
PTH is what kind of amino acid?
An 84 polypeptide amino acid
What is the effect of PTH on bones?
Increase activity of osteoclasts causing calcium release from bones
What are the effects of PTH on the kidneys?
- Increase calcium reabsorption from urine.
- Increases urinary phosphate excretion.
- Increases renal production of 1,25 (OH) D (Vitamin D3), which causes increased GI absorption of calcium
What population is most at risk for hyperparathyroidism?
Age early 50’s & Female
What is the most common cause of outpatient hypercalcemia?
Primary hyperparathyroidism
What is the major cause of primary hyperparathyroidism?
85% caused by single adenoma
What are the 3 causes of primary hyperparathyroidism?
- Single adenoma,
- diffuse hyperplasia,
- multiple adenomas
What are the S/S of hyperparathyroidism?
- Stones, bones, groans, moans
- (renal, skeletal, abdominal, cardiovascular, psychiatric & neuromuscular)
What are the neuropsychiatric S/S of hyperparathyroidism?
- Easy fatigue.
- Depression.
- Inability to concentrate.
- Memory problems.
- Proximal myopathy (symmetric weakness in muscles close to body’s center)
What does bisphosphonate do?
It lowers calcium but may increase PTH
What does Cinacalcet do?
- It lowers calcium but only modestly lowers PTH.
- It does not decrease calcium excretion.
What is the downside to parathyroid imaging?
All are very poor at multi-gland disease
What is done for a patient who presents for parathyroidectomy and has an increased calcium level?
Dilute calcium with NS and maybe give loop diuretic.
What kind of ventilation is avoided intraop for a Pt undergoing parathyroidectomy & why?
- Hypoventilation
- acidosis can lead to increased ionized calcium → cardiac arrhythmias
How is a parathyroid crisis managed?
- Hydration to dilute calcium.
- Diuresis with loop diuretics.
- Glucocorticoids,
- calcitonin,
- dialysis
What is the half-life of PTH?
~ 4mins
When are PTH levels drawn?
- At baseline before incision.
- During manipulation of the suspected gland.
- 5, 10, 20 mins after gland excision.
What is indicative that all offending glands have been removed?
A PTH decline of >50% from baseline
What innervates the larynx sensory above the vocal cords?
Internal branch of the SLN
What innervates the larynx sensory below the vocal cords?
Recurrent laryngeal nerve
What & where is released in response to increased calcium & how does it work?
- Calcitonin from the parafollicular cells.
- Inhibits osteoclastic activity in the bones & inhibits renal tubular cell reabsorption of calcium.
