endocrine disorders Flashcards
hormone producing cells of thyroid gland
follicular cells and parafollicular cells
follicular cells
produce, store and release thyroxine (t4) and triiodothyronine (t3) (active forms); major regulators of the basal metabolic rate
parafollicular cells “c cells”
secrete calcitonin, hormone that has minor role in maintaining calcium homeostasis
what is the rate limiting step in thyroid hormone synthesis
follicular cells capturing iodide from circulation
s/sx of thyroid nodule
pain, pressure, or hoarseness may suggest local invasiveness and should be assessed
evaluation of thyroid nodule/mass
palpate while pt swallows; indirect/direct laryngoscopy (hoarseness,pain, malig); TSH test and thyroid function test; serum Ca levels (hx radiation or MEN); FNA*; US
what does low level tsh suggest
thyrotoxicosis
what does high level of tsh suggest
underactivity (assoc w Hashimoto’s thyroiditis)
what does thyroid function test include
TSH and T4, sometimes T3
if pt has Grave’s ds what thyroid tests should be ordered
t4, t3, tsh, tbg, tsab only if toxic symptoms
pt related to someone w men2 should have what test
urinary catecholamines and catecholamine metabolites screened for functional pheochromocytoma
what is the only thyroid cancer that reliably expresses a tumor marker that is measurable in serum (calcitonin)
medullary carcinoma
pheochromocytoma
neoplasm of the adrenal medulla; arises from chromaffin tissue of neural crest origin; secretes excess epinephrine, norepinephrine, dopamine, or other vasoactive amine; causes a constellation of signs and symptoms as a result of catecholaminemia; associated with the familial endocrine syndromes multiple endocrine neoplasia types 2A (MEN-2A) and 2B (MEN-2B)
single most important study in evaluating a thyroid mass
fine needle aspiration cytology
grading system of fna of thyroid nodule
follicular cells (5% risk), follicular cells w atypic (25%), suspicious for papillary carcinoma (75-95), papillary carcinoma (100%)
tx solid thyroid nodule low risk for malignancy on fna
observation 3-6m while on oral thyroid hormone to suppress TSH stimulation of tumor growth (suppress to mid-low range w careful monitoring); remains same size then reaspirated; larger=excised
suppression TSH to very low levels inc risk for
osteoporosis and new onset atrial fibrillation
tx thyroid nodule w cancer
thyroid lobectomy and isthmectomy to remove ipsilateral lobe of thyroid gland along with isthmus; or complete thyroidectomy removes the full tumor
why should frozen sample of thyroid not be used to analyze for cancer
causes great deal of distortion and dx is often subtle
performing lobectomy or total thyroidectomy, great care is taken to preserve what
parathyroid glands and their blood supply; recurrent laryngeal nerve and external branch of superior laryngeal nerve (voice quality)
injury to recurrent laryngeal nerve during thyroid lobectomy causes
paralysis of ipsilateral vocal cord which becomes immobile in paramedic position; leaves pt w weak, breathy voice; (if thyroidectomy b/l injury causes loss of speech and airway control and requires tracheostomy)
mc cause of hyperthyroidism
Grave’s ds or diffuse toxic goiter
Grave’s ds
autoimmune thyrotoxicosis
goiter
thyroid enlargement
toxic multinodular goiter
thyroid enlargement from multiple nodules that may cause compression symptoms
diffusely enlarged, soft gland w homogeneous increased radionuclide uptake and no nodules
Grave’s ds
solitary nodule w inc uptake against background of suppressed uptake in remaining thyroid
toxic adenoma
diffusely multinodular gland, heterogeneous radionuclide uptake, and multiple nodules of varying sizes on us
toxic multinodular goiter
hyperthyroidism, exophthalmos tachycardia, tremor; heat intolerance, wl
graves; result from excessive production of thyroid hormone
s/sx of hyperthyroidism
nervousness, restlessness, emotional lability, fast speech, fine tremor, tachycardia, palpitations, arrhythmias, dyspnea, lid lag, proptosis, exophthalmos, ophthalmopathy, inc sweating, fatigue, weakness, hair loss, leg swelling, pretrial myxedema
what can determine is hyperthyroidism is pituitary dependent or independent
serum TSH levels: tsh dec w thyroid and inc w pituitary;
hyperthyroidism assoc w Graves ds is caused by
circulating immunoglobulin G (IgG), immunoglobulin (thyrotropin receptor antibody [TRAb]) that is directed against the TSH receptors on the follicular cells of the thyroid. This antibody stimulates the thyroid to generate and secrete thyroid hormone, but the sensitivity to the negative feedback system that controls normal thyroid function is lost. Thus, TRAbs causes excessive production of T3 and T4 and progressive hyperthyroidism. The pathogenesis of the exophthalmos and the pretibial myxedema of Graves’ disease is the result of expression of TSH receptors by the retro-orbital tissues
tx Graves
medical blockade of hormone and se; radio iodine ablation of active thyroid tissue; surgical resection;
medical blockade of hormone and se in graves
iodide and propranolon role in short term or preop prep but not definitive; thionamides (propylthiouracil “put”, methimazole “tapazole”) 6-12m but has sig se
se of thionamides
recurrent/persisten hyperthyroidism; intolerance of meds including cholestasis, arthralgia, headache, neuritis, dependent edema; reversible agranulocytosis
radioablation for graves
isotope is 131I at dose of 80muCi/g; 2nd/3rd dose if hyperthyroidism after 6m; safe and effective; completely destroys cells rather than altering DNA
solitary tumor of the thyroid gland that produces excessive amounts of thyroid hormone and causes clinically overt hyperthroidism
toxic adenoma
how does thyroid adenoma present
similar to graves with exception of ophthalmopathy or pretrial myxedema because it is not an autoimmune ds
eval differing graves and toxic adenoma
Serum thyroid hormone levels show high T3 and T4 and suppressed TSH, consistent with an autonomous thyroid source of the excessive thyroid hormone production. The differentiation between hyperthyroidism caused by Graves’ disease and that caused by toxic adenoma depends on the characteristics of the thyroid on physical examination and scan. In patients with Graves’ disease, the thyroid is diffusely enlarged. In patients with toxic adenoma, it is normal or small, with a palpable nodule that is “hot,” or functional, on thyroid scan.
tx toxic adenoma
After preoperative preparation, usually with propranolol or one of the thionamides, the lobe with the “hot” nodule is excised by thyroid lobectomy and isthmectomy. Surgery is also considered optimal therapy for a toxic multinodular goiter (Plummer’s disease). Total thyroidectomy is indicated, especially if the goiter is large and associated with symptoms such as compression
Plummer’s ds
toxic multinodular goiter
auto dom condition caused by mutation of RET
familial medullary thyroid carcinoma
cancers from follicular cells
(papillary and follicular varieties) well differentiated thyroid cancers; hurthle or oxyphil cell tumors; anaplastic tumors
parafollicular cell cancers
medullary carcinoma (lymphoid cells to lymphoma)
mc thyroid malignancy in US
papillary carcinoma
tumors w a mix of papillary and follicular features are classified how
as papillary cancers because they have similar biologic behavior
what are papillary carcinomas characterized by
concentric layers of calcium (psammoma bodies) found in the stalk formations
papillary cancers grow slow so have excellent prognosis but when does it have a poor prognosis
males, >50yo, primary tumor >4cm, less well differentiated cells, locally invasive or distant metastatic ds
tx papillary carcinoma
lobectomy or total thyroidectomy based on AMES/AGES; lymph node removal if involved; thyroid hormone replacement
distant metastases of papillary carcinoma
lungs and bone; radio iodine
monotonous, relatively uniform appearance of micro follicles; presence of capsular and vascular invasion; slow growing
follicular carcinoma
poor prognostic indicators for follicular carcinoma
> 45yo, local invasion to contiguous neck structures and distant metastases
tx follicular carcinoma
lobectomy or total thyroidectomy based on AMES/AGES; lymph node removal if involved; thyroid hormone replacement
genetically transmitted, auto dom inheritance assoc w familial medullary carcinoma or men type 2a or 2b
medullary carcinoma
location of tumor in pt w fam med cancer or men
both thyroid lobes
location of medullary thyroid carcinoma (MTC)
one lobe; worse prognosis than pap/foll carcinoma
dx medullary cancer
plasma screening that shows elev calcitonin levels or by screening w a calcium and pentagastrin infusion test that shows elev calcitonin
MTC tx
total thyroidectomy and central (level VI) lymph node dissection (removal of cervical lymph nodes medial to both recurrent laryngeal nerves and carotid arteries)
extremely aggressive neoplasm arises from follicular cells
anaplastic carcinoma; survival
how to distinguish lymphoma from hashimoto’s thyroiditis
core needle or open bx
hashimoto’s thyroiditis
autoimmune thyroiditis
yellow brown, ovoid, soft and mobile; attached fatty tissue
parathyroid glands- endocrine glands in neck that secrete parathyroid hormone
parathyroid glands are usually 5mm, what happens as they become larger
darker brown, firm and less fatty
what are the parathyroid glands a sole source of
parathyroid hormone (84 amino acid peptide)
PTH and calcium
hypocalcemia stimulates PTH while hypercalcemia inhibits PTH
roles of PTH
PTH directly increases calcium resorption in the proximal convoluted renal tubule. PTH increases phosphate clearance, but PTH secretion is not influenced by serum phosphate levels. PTH directly mobilizes calcium from bone and stimulates osteoclast activation and bone reabsorption. PTH indirectly increases gastrointestinal calcium absorption by stimulating vitamin D production.