Endocrinology Flashcards
What is the typical strategy for thyroid hormone replacement and hypothyroidism?
“Two strategies may be used (1) start with 25 μg daily and titrate up every 1–2 months until the TSH is in the normal range or (2) start with full-dose therapy based on weight (1.6 μg/kg daily) and adjust based on TSH in 1–2 months. Either option is appropriate in young, otherwise healthy adults. But older patients (>65 years old) or those with multiple comorbidities should be started at a low dose (25 μg daily). If the patient is titrated up to 200 μg of levothyroxine and does not seem to be responding, the diagnosis needs to be reconsidered or the patient’s compliance needs to be carefully assessed. Iron and food will decrease the absorption of levothyroxine by as much as 40%. It usually takes 6–8 weeks for the body’s endocrine response and TSH to reach a steady state”
Name three symptoms of hypothyroidism.
“The history given is consistent with a hypothyroid state. Symptoms of hypothyroidism include thinning hair, dry skin, a hoarse, deep voice, bradycardia, and a prolonged relaxation in the reflexes.”
What is Graves’ disease?
“The family history, the symptoms and signs of hyperthyroidism (especially the diffusely enlarged goiter with a bruit), and the exophthalmos are all typical. Conjunctival injection is also frequently noted”
What is viral hyperthyroidism and how is it treated?
“Viral thyroiditis can cause hyperthyroidism and a goiter, but the thyroid gland is usually tender. Also, viral thyroiditis will likely not last 4 months, but is usually self-limited to <6 weeks”
“75% of patients with viral thyroiditis will progress from 2 weeks of self-limited hyperthyroidism to 3–6 months of hypothyroidism that is also self-limited. The hyperthyroid phase is best treated with NSAIDs, beta-blockers, and prednisone if needed.”
What should be the immediate management of hyperthyroidism?
“There is no need to wait before starting methimazole (Tapazole), which blocks production of thyroid hormone. PTU can also be used but methimazole is preferred because (1) it affords better control and (2) PTU is associated with more liver toxicity and bone marrow suppression (although these adverse effects can occur with both drugs). PTU is still preferred during pregnancy. Propranolol is helpful for controlling the symptoms of hyperthyroidism (tachycardia, tremor, etc) and prevents the conversion of T4 to active T3”
What is a thyroid storm?
“The syndrome of thyroid storm is characterized by fever, tachyarrhythmias, altered mental status, and high output cardiac failure. It is induced by a major stress (infection, surgery, myocardial infarction, etc.) in a patient with underlying hyperthyroidism (usually undiagnosed).”
Name three signs of thyroid storm.
A) Hyperthermia. B) Right upper quadrant pain. C) Diffuse muscle weakness. D) Atrial fibrillation. E) Hypomania, confusion, other central nervous system (CNS) signs and symptoms.
right upper quadrant pain, is from liver congestion secondary to high output congestive heart failure (CHF) and is a bad sign”
What is the appropriate treatment for thyroid storm?
“extremis (hypotensive and tachycardic) and needs fluid hydration, despite pulmonary edema. Cooling measures address hyperthermia, and beta-blockade (propranolol) will improve high output failure (and reduce the pulmonary edema). Corticosteroids help block release of thyroid hormone and decreases peripheral conversion of T4 to T3. Additionally, corticosteroids will treat any underlying adrenal insufficiency. Methimazole prevents thyroxine synthesis. This must be given before iodine. The iodine blocks any further release of thyroid hormone”
Where is the likely diagnosis for a patient that has all the signs and symptoms of hyperthyroidism but a low TSH and normal T4?
“Five percent of patients with hyperthyroidism have an isolated T3 hyperthyroidism. Thus, if you suspect hyperthyroidism and the patient has a low TSH but a normal free T4, check a T3-RIA”
Name a medication that can cause hyperthyroidism.
“Amiodarone (see Helpful Tip) and Peginterferon Alfa-2a can cause hyperthyroidism.
Amiodarone is interesting because it can cause hyperthyroidism or hypothyroidism. It has multiple effects on the thyroid gland and on metabolism of T4 and T3, which can result in hypothyroidism. It carries a huge iodine load, which can result in hyperthyroidism. Somewhere between 2% and 30% of patients taking amiodarone will have thyroid dysfunction. Amiodarone is highly lipophilic and may have a half-life as long as 100 days, resulting in toxicity long after the drug is stopped”
How do you make a definitive diagnosis of a thyroid nodule?
“FNA can conclusively prove or disprove the presence of neoplasm and should be considered for all thyroid nodules and cysts”
“A “hot” nodule may cause hyperthyroidism, is usually nonmalignant (“hotis not”) and can be treated with I131. A cold nodule is either an adenoma or a malignancy and a biopsy is mandated”
What is the appropriate treatment for the thyroid adenoma as identified by a biopsy?
“Surgery for removal of the tumor is the most appropriate next step, but a CT scan is indicated to delineate the extent of the neoplasm.”
“Radiotherapy with I131 is used after surgery for metastatic disease, but external beam radiation is not used for thyroid cancers except for the palliative therapy of anaplastic carcinoma. Because these tumors are TSH responsive, suppression of TSH level following surgery for papillary carcinoma is achieved with thyroxine (usually 2.2–2.5 μg/kg—fairly high dose to completely suppress TSH production)”
The patient comes in a seemingly manic and a breast masses found physical examination. What kind of changes might be expected on EKG?
“This patient is likely to have hypercalcemia, probably from an undiagnosed metastatic breast cancer. The ECG in a patient with significant hypercalcemia will show a short QT interval; rarely there is diffuse ST elevation. Hypocalcemia is associated with a long QT interval, which can occasionally lead to arrhythmias due to an R on T phenomenon (an R-wave of a PVC fuses with the previous T-wave predisposing to torsades de pointes). Hypercalcemia produces symptoms in the CNS (confusion, psychosis, depression), GI system (abdominal pain, cramps, constipation), kidneys (nephrolithiasis, polyuria, renal insufficiency), and musculoskeletal system (weakness, myopathy, osteoporosis). To help you remember the symptoms of hypercalcemia, use the phrase “stones, bones, moans, groans, and psychiatric overtones”
Excerpt From: Mark Graber & Jason Wilbur. “Family Practice Examination and Board Review, Third Edition.” McGraw-Hill Medical, 2013. iBooks.
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What is the emergent treatment for hypercalcemia?
Saline IV, adequate hydration and establishing urine output is critical to the treatment of hypercalcemia and should be the next step. A normal saline infusion will increase urinary calcium excretion by inhibiting proximal tubular sodium and calcium reab-sorption. Note that IV furosemide (and diuretics in general) are falling out of favor and should not be used. Hydration is the most important goal. An IV bisphosphonate infusion should then be started and will lower the calcium level over 2–4 days. Calcitonin has a limited duration of action and can be used in emergencies where saline is ineffective”
How can a chronically elevated hypercalcemia be treated when it’s from metastatic disease?
“Glucocorticoids decrease intestinal calcium absorption, but in and of themselves can lead to bone density loss and an increased risk for fractures. Oral phosphates can decrease intestinal calcium absorption and bone reabsorption of calcium. Bisphosphonates, as previously discussed, decrease the serum calcium and increase bone density”
Elevated parathyroid hormone in the presence of hypercalcemia is indicative of which disease?
“This patient has primary hyperparathyroidism. He has an elevated parathyroid hormone in the presence of hypercalcemia. This is usually caused by a functional parathyroid adenoma and is best treated in otherwise healthy patients with a parathyroidectomy. This can be done without significant loss of thyroid tissue. In elderly patients with mild hyperparathyroidism and asymptomatic hypercalcemia, medical management is an option. If the patient had a low or normal PTH level, occult cancer should be considered (check for PTH-like hormone in the serum), and a bone scan or body CT may be warranted”
A rare complication of removal of too much parathyroid gland may result in which disease that results in increased muscle spasms and fatigue?
“This patient likely has hypocalcemia due to excessive removal of parathyroid gland tissue. This is a rare, but unfortunate, complication of parathyroid gland removal and is usually detected in the immediate postoperative course. The patient’s physical exam demonstrates Chvostek sign (tapping over the facial nerve elicits a twitch) and Trousseau signs (carpopedal spasm after placement of a blood pressure cuff). Vitamin D deficiency, although a cause of hypocalcemia, is unlikely to develop so quickly”
Do you have to correct for hypoalbuminemia when determining serum calcium level?
Yes. “To correct for albumin, add 0.8 mg/dL to the serum calcium level for each 1 g/dL the albumin is <4g/dL. In other words, corrected serum calcium = [(4-albumin) × 0.8] + measured serum calcium, or in this case the equation is [(4–3) × 0.8] + 5.1 = 5.9 mg/dL”
