Endocrinology Flashcards
Lab values virtually diagnostic of a prolactinoma
Prolactin > 200, low testosterone with low/inappropriately normal LH +/- low TSH depending on compressive symptoms.
Why does prolactin rise in patients with primary hypothyroidism?
The increased secretion of TRH in response to low T4 also results in an increased stimulation of lactotrophs and elevated prolactin
Ca levels in patients with hypercalcemia secondary to malignancy?
> 13
Substances that can chelate calcium and cause symptomatic hypocalcemia?
Citrate (typically only seen in patients with liver failure that cannot rapidly metabolize citrate before it can chelate Ca)
Lactate
Foscarnet
EDTA
Phenytoin
Bisphosphonates
Why might patients being treated for eclampsia develop symptomatic hypocalcemia?
Mg infusion and hypermagnesemia can turn off PTH release from the parathyroids, reducing serum Ca levels.
3 forms of Ca in the blood
Albumin-bound, ionized and bound to organic and inorganic acids.
Why might a patient who is hyperventilating or vomiting repetitively have symptomatic hypocalcemia?
Both of these conditions cause alkalemia, which results in H+ dissociation from albumin and increased Ca binding to albumin.
Why are prolactin levels often elevated even when patients have a non-functioning pituitary adenoma?
The mass effect disrupts dopaminergic pathways in the brain, reducing the inhibitory effect dopamine has on pituitary lactotrophs.
How does excessive alcohol intake cause hypogonadism?
It directly inhibits testicular testosterone production and reduces pituitary LH secretion.
A patient presents with muscle atrophy of the hip flexors and quadriceps, high-frequency low-amplitude tremor worse with movement and increased reflexes with shortened relaxation phase.
Thyrotoxic myopathy
Diagnostic criteria for DKA
pH 250
+Plasma ketones
How many days of immobilization can it take to develop hypercalcemia in a patient with renal failure?
3
Infections that can result in primary adrenal insufficiency
CMV, fungal infections and Tb.
Most common congenital cause of primary adrenal insufficiency?
Adrenoleukodystrophy. This happens secondary to inability to properly metabolize VLCFAs, which accumulate in the adrenals.
When to discontinue antithyroid medications due to agranulocytosis?
WBC
Why are symptoms less severe in patients with secondary adrenal insufficiency?
They typically have preserved aldosterone production, so the hyperkalemia, hypotension and hyperchloremic metabolic acidosis are not as prominent as it would be if there were no mineralocorticoid function.
Lab values seen in patients with osteomalacia due to vitamin D deficiency?
Low Ca absorption from vitamin D deficiency results in hyperparathyroidism, Ca retention and PO4 excretion. Consequently, there is greater hypophosphatemia, relative hypocalcemia and elevated alk phos due to bone resorption.
Plasma aldosterone to renin ratio that suggests primary hyperaldosteronism
> 20 with aldosterone concentration > 15
Diagnostic criteria for metabolic syndrome
3/5 criteria:
1) Waist > 40 in men and 35 in women
2) FBG > 100-110
3) BP > 130/80
4) TGs > 150
5) HDL
Contraindications to radioactive iodine therapy for Grave’s disease
Pregnancy and ophthalmopathy
Diabetic medication to add to metformin if the patient needs to lose weight
GLP-1 agonists: exenatide and liraglutide
What patients may be considered for prophylactic total thyroidectomy
Those with RET protoncogene mutations that may lead to MEN2 syndromes. This mutation results in 90-100% incidence of medullary thyroid carcinoma.
Promotility agents used to manage patients with diabetic gastroparesis
Metoclopramide (look out for extrapyramidal symptoms)
Erythromycin (IV for acute exacerbations)
Cisapride (not in US)
Beta-blocker that may be amenable to use in patients with pheochromocytoma?
Labetolol has both alpha and beta blocking effects, which would not result in unopposed alpha-mediated vasoconstriction that is seen with beta-blockers that don’t touch alpha receptors.
Why do patients with ectopic-ACTH production often have hypertension and hypokalemia?
Typically cortisol is inactivated by the enzyme 11-beta HSD to cortisone. However, when there are exceedingly high levels of cortisol as seen in ectopic-ACTH producing tumors, the excess cortisol activates mineralocorticoid receptors.
Diagnostic criteria for PCOS
2/3 criteria:
Androgen excess (hirsutism, acne, alopecia)
Oligo or an ovulation
≥ 12 ovarian follicles and/or ovarian volume > 10mL
AND: other causes of hyperandrogegism such as non-classic CAH, hypothyroidism, hyperprolactinemia, Cushing syndrome and androgen secreting tumors have been ruled out.
When is metformin recommended for patients that do not meet criteria for diabetes, but demonstrate insulin resistance?
BMI > 35
Treatment of complications associated with PCOS?
DM = weight loss and metformin
Hyperandrogenism = OCPs decrease adrenal androgen production, increase SHBG production in the liver and inhibit LH secretion
Infertility = clomiphene
Who gets BRCA testing
History of ovarian or breast cancer in a first or second degree relative who was diagnosed when they were
Side effects of antithyroid medications
Methimazole = 1st trimester teratogen + agranulocytosis
PTU = agranulocytosis, liver failure and ANCA-associated vasculitis
Who should be screened for diabetes?
USPSTF = sustained BP > 135/80
ADA = all adults ≥ 45 years old and those with risk factors
Who should be screened for lung cancer?
Adults 55-80 with ≥ 30 years smoking history who currently smoke or have quit in the last 15 years