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
Who should get PAP smears?
Women age 21-29 every 3 years
Women 30-65 can get them every 5 years if they have concurrent HPV testing, or continue PAP alone every 3 years.
3 characteristic features of hypopituitarism
Glucocorticoid deficiency (with preserved mineralocorticoid because it is ACTH independent)
Testosterone deficiency
Hypothyroidism
Less intuitive causes of hypopituitarism
Hemochromatosis
Lymphocytic hypophysitis
Sarcoidosis
TB
Patients with Paget’s disease who do not require bisphosphonates
Asymptomatic patients with disease involving non-weight bearing bones
Pituitary microadenoma definition
Who gets treated with dopamine agonists for prolactinomas?
Macro adenomas and symptomatic patients
Prussian blue in urine after a patient takes an antibiotics
G6PD deficiency.
Drugs that can cause autoimmune hemolysis due to anti-RBC IgG crossover
Alpha-methyldopa and penicillin
Measure corrected calcium
Ca + (0.8 x (4 - Albumin))
Patient presents with diabetes, weight loss, diarrhea, anemia and erythematous papules/plaques that coalesce to form large painful areas with central clearing.
Glucagonoma with necrolytic migratory erythema.
How to confirm glucagonoma
Serum glucagon > 500
Why do people with hyperthyroidism get accelerated bone loss?
Thyroid hormone increases osteoclast activity leading to hypercalcemia, reduced PTH secretion and net calcium loss.
Most common type of thyroid cancer
Papillary (> 70%)
Where do papillary thyroid cancers metastasize to?
Regional lymph nodes. Follicular thyroid cancers metastasize hematogenously.
Pathophysiology behind Addison’s disease
Antibodies form against one or more adrenal enzymes involved in steroid synthesis
Primary intervention to help reduce kidney damage in patients with diabetic nephropathy
The first change in diabetic nephropathy is glomerular hyper filtration and microalbuminuria. To reduce hyper filtration blood pressure control to
Most common cause of death in patients with acromegaly
Cardiovascular
Thyroid cancer you cannot diagnose with FNA
Follicular. The cells classically look normal, but you need to see if there is extra capsular extension
Histopathologic features of papillary thyroid cancer
Psammoma bodies and orphan Annie nuclei
When should you start supplementing patients in DKA with K+?
Once the K+ gets down to 4.5 on insulin + IVF alone.
Malignancies that can produce PTHrP? Malignancies that cause hypercalcemia via other mechanisms?
PTHrP: SCC of lung, H&N, esophagus. Renal and bladder cancer. Ovarian and endometrial cancer. Breast (local production in bone).
Vitamin D: lymphomas
Bony mets with local cytokine production: breast, multiple myeloma and lymphoma
How long before HPA axis regains normal function after chronic glucocorticoid use?
6-12 months
Way to administer estrogen without decreasing LT4 levels
Transdermal patch. This bypasses the liver and will not increase thyroid binding globulin levels like OCPs do.
Benefits if tight glycemic control in diabetics
Only seen with microvascular complications, not macrovascular. Mortality increases if A1c goal is
What patients should receive eplerenone for primary hyperaldosteronism?
Those with bilateral adrenal hyperplasia or unilateral adrenal adenoma and not surgical candidates.
How does CKD result in secondary hyperparathyroidism?
Decreased hydroxylation of Vit D leads to decreased Ca levels and increased PTH. Additionally, decreased tubular function results in PO4 retention and Ca sequestration as CaPO4, further promoting PTH secretion.
Patient presents with watery diarrhea, achlorhydria, hypokalemia, hypercalcemia, hyperglycemia and secretory diarrhea with increased stool Na and osmolar gap
This patient has a VIPoma. VIP binds intestinal epithelial cells and promotes fluid and electrolyte secretion into the lumen. They have achlorhydria due to inhibition of gastric parietal cells, hypokalemia due to K+ loss in stool, hyperglycemia due to increased glycogenolysis and hypercalcemia due to increased bone resorption. Confirm diagnosis with VIP level > 75 and CT showing tumor in pancreas tail.
Surgical candidates for hyperparathyroidism
Ca > 1 over upper limit of normal
Age
Treatment of thyroid storm
Beta-blockers
PTU
Iodine to limit hormone release
Glucocorticoids to limit T3 -> T4
4 main substrates of gluconeogenesis
Lactate
Alanine
Glutamine
Glycerol-3-P
Most common testicular sex cord stromal tumor
Leydig
Euthyroid sick syndrome
Normal T4 and TSH with reduced total and free T3 levels. This is thought to be due reduced peripheral conversion of T4 to T3 due to caloric deprivation, elevated glucocorticoid levels, elevated cytokine levels and 5’ monodeiodinase inhibitors.
Subclinical hypothyroidism labs
Elevated TSH, normal T4
Best marker for resolution of ketonemia in patients with DKA?
Direct assay of beta-hydroxybutyrate and serum anion gap
What does the nitroprusside test measure?
Acetoacetate and acetone, not beta-hydroxybutyrate
How is vitamin D absorbed in the intestines?
Via chylomicrons, this is why people with steatorrhea can get osteomalacia/rickets
Why are alcoholics at risk for hypocalcemia?
They lose Mg in their urine, diarrhea, have malnutrition and get acute pancreatitis. Hypomagnesemia causes PTH resistance and non-responsive hypocalcemia.
What patients are at high risk to get diuretic-induced hypokalemia?
Those with mild primary hyperaldosteronism
How to evaluate for hyperandrogenism due to the adrenals and not the gonads?
DHEA-S is the only androgen produced specifically by the adrenal glands.
Effective plasma osmolality
Excluded BUN from the equation because it crosses both intravascular and extravascular compartments:
2Na + Glc/18
Corrected Na+
Na + 2 for each mg/dL glc is over 100
Metabolic abnormalities that go along with hypothyroidism
Hyperlipidemia (decreased surface LDL-Rs)
Hypertriglyceridemia (decreased LPL activity)
Hyponatremia (decreased free water clearance)
Elevated CK
Transaminitis
Anemia (reduced RBC mass)
AUA PSA screening recs?
Ages 40-75 as long as there is 10 year life expectancy
Absent or decreased Achilles reflex in elderly
Normal loss due to decreased muscle done
When is postpartum vaginal bleeding abnormal?
8 weeks post-partum
Gestational trophoblastic neoplasia vs. choriocarcinoma?
GTN = localized Choriocarcinoma = mets to lungs
Lab findings in patients with anti-phospholipid antibody syndrome
VDRL +, thrombocytopenia and prolonged aPTT
4 causes of priapism
Sickle cell disease
Cavernous artery trauma
Spinal cord injury
Meds (trazodone, prazosin)
