Endocrinology Flashcards
What is meant by positive and negative feedback regulation in endocrine diseases?
Positive feedback refers to the stimulation of hormone secretion by the feedback mechanism, and in negative feedback hormone secretion is inhibited by the feedback.
What are the definitions of primary, secondary, and tertiary hormone diseases?
Primary glandular failure refers to disease of the gland that secretes the hormone. Secondary glandular disease is disease of the gland that controls the primary gland. Tertiary glandular disease is disease of the gland that controls the secondary gland that controls the primary gland.
What are the hormones of the anterior pituitary?
The hormones of the anterior pituitary gland include FSH, LH, TSH, ACTH, GH, and prolactin.
What are typical signs and symptoms of a pituitary tumor?
Historically, pituitary tumors presented with hormonal hypersecretion symptoms, hypopituitarism, and mass effect. Now, with the use of imaging, these are frequently found incidentally in imaging done for other reasons.
Aside from prolactinoma, what are the other causes of hyperprolactinemia?
Non-prolactinoma causes of hyperprolactinemia include drugs (antipsychotics, metoclopramide, and verapamil), Diseases of the hypothalamus or pituitary stalk which interfere with production or transport of dopamine (sarcoidosis, trauma), pregnancy, nipple stimulation, orgasm, chest wall injuries (piercing, shingles), hypothyroidism, and chronic kidney disease.
What is the best initial medical therapy for hyperprolactinemia?
Cabergoline is the 1st line treatment for hyperprolactinemia. This is contraindicated in known lung, heart valve, and retroperitoneal fibrotic disease. Bromocriptine is the 2nd line treatment for hyperprolactinemia, but it causes more nausea and orthostatic hypotension than cabergoline.
How do you test for acromegaly?
Screen for acromegaly with IGF-1. Growth hormone measurement is not recommended because its secretion is pulsatile and levels can fluctuate greatly.
What is the workup for pituitary incidentaloma?
The size of an incidentally found pituitary tumor depends on size. If it is <1cm evaluate for hormone hypersecretion. If >1cm evaluate for hormone hyper- and hyposecretion as well as evaluation of visual fields. To test for hypersecretion check prolactin, IGF-1, 24-hour urinary free cortisol or low-dose dexamethasone suppression test, and check TSH and free T4. Test for hyposecretion with TSH, free T4, morning cortisol, LH, FSH, and estradiol.
Which cancers metastasize to the pituitary?
Lung and breast cancers are the most common cancers to metastasize to the pituitary.
What is the clinical presentation of pituitary apoplexy? The treatment?
Pituitary apoplexy is caused by hemorrhage in a pituitary mass. It presents with severe headache, N/V, visual defects, and altered mental status. If symptoms are mild only corticosteroids may be necessary. Edema causing mass effect requires emergent neurosurgical decompression.
What happens to the urine osmolality and serum sodium in a patient with diabetes insipidus who is on a water restriction?
A DI patient on water restriction will have an elevated serum sodium and will continue to put out a dilute urine.
What are the urine osmolality, serum sodium, and serum osmolality in a patient with SIADH?
A patient with SIADH will have a concentrated urine, high urine sodium excretion, low serum sodium, and low serum osmolality.
What is the first screening test of choice for hyper- and hypothyroidism?
The first screening test for hypo- and hyperthyroidism is a TSH.
What is the difference between the thyroid uptake and the thyroid scan? What do the different tests tell you?
The thyroid uptake measures the degree of iodine uptake in percent uptake whereas the thyroid scan (scintigraphy) assesses the pattern of uptake.
What are the common signs and symptoms of hypothyroidism? Lab tests?
The common symptoms of hypothyroidism are cold intolerance, weight gain, fatigue, menstrual irregularities, mental slowness, depressed mood, constipation, hoarseness, edema, brittle nails. Common signs are goiter, cool/pale skin, coarse hair, periorbital or nonpitting edema, delayed reflexes, and bradycardia.
How do you make a diagnosis of secondary or tertiary hypothyroidism?
Secondary and tertiary hypothyroidism are diagnosed by a low TSH and low free T4, once euthyroid sick syndrome is excluded.
What are the risks of overtreating hypothyroidism?
The risks of overtreating hypothyroidism include bone loss, tachyarrhythmias (atrial fibrillation).
What are the signs and symptoms of myxedema coma?
Patients with myxedema coma present with progressive symptoms of hypothyroidism. Decreased mentation and hypothermia are the classic findings.
What is the treatment of myxedema coma?
Myxedema coma is treated with thyroid hormone (most experts recommend combined T4 and T3). Glucocorticoids should be given as well until adrenal insufficiency is ruled out.
What is apathetic hyperthyroidism?
Elderly patients may present with atrial fibrillation or depression without classic symptoms of hyperthyroidism. This is termed apathetic hyperthyroidism.
What specific physical findings confirm the diagnosis of Graves disease?
Physical findings consistent with Graves disease include diffuse goiter (sometimes with a bruit) and Graves ophthalmopathy (proptosis and periorbital edema).
What is the result of the thyroid uptake and scan in a patient with Graves disease?
The thyroid uptake and scan in Graves shows increased uptake in a diffuse pattern.
What are the side effects of medications used to treat Graves disease?
Graves disease is treated with methimazole and PTU. Methimazole cannot be given in the 1st trimester of pregnancy. PTU is associated with liver injury, vasculitis, and lupus-like syndrome. Both PTU and methimazole can cause hepatic toxicity and agranulocytosis.
What are the precipitating events leading to thyroid storm?
Precipitating events for thyroid storm include surgery, infections, or an iodine load (amiodarone or contrast).
In addition to PTU or MMI, beta-blockers, and iodine, which other drug is given to patients to treat thyroid storm?
Thyroid storm is generally associated with a relative adrenal insufficiency. Therefore, glucocorticoids should be added to treatment with PTU or MMI, beta-blockers, and iodine.
What causes subacute thyroiditis?
Subacute thyroiditis is presumed to be caused by viral infection causing granulomas in the thyroid gland.
What are the results of the thyroid uptake in patients with thyroiditis (all causes)?
Thyroid uptake is reduced in patients with thyroiditis of all causes.
In which situations is it appropriate to check a sick patient’s thyroid function?
Do not check thyroid studies in sick patients unless their illness is likely to be caused by myxedema coma or thyroid storm.
Workup of which nodule can cease after the thyroid uptake and scan - a hot or cold one?
A hot nodule on thyroid uptake and scan does not require further workup.
List some characteristics associated with malignant nodules.
Malignant nodules are usually cold on thyroid scan. However, most benign nodules are also cold.
If the TSH is high and an ultrasound of a solitary nodule is not concerning for malignancy, what is the most common diagnosis?
Hypothyroidism is the most common cause of a benign appearing nodule (on ultrasound) with a high TSH.
What are the 4 histologic types of thyroid cancer? Which is the most aggressive?
The four types of thyroid cancer are papillary, follicular, medullary, and anaplastic. The most aggressive is anaplastic thyroid cancer.
What is the hormone released by medullary thyroid cancer?
Medullary thyroid cancer is associated with an elevated calcitonin secreted by parafollicular C cells.
MEN2A and MEN2B are associated with which histologic type of thyroid cancer?
MEN2A and MEN2B are both associated with medullary thyroid cancer.
What is the gene associated with medullary thyroid cancer?
Medullary thyroid cancer is associated with point mutations in the RET oncogene.