ENDOCRINE Flashcards
most common type of thyroid cancer radiation-induced
papillary.
Subsequent development of thyroid neoplasia is associated with a dose of 5 to 20 cGy.
The risk is lower with higher levels of radiation!
[ probably because of the cytotoxic effect of higher doses ]
The latency period has been reported to be as long as 40 years.
gold standard in initial evaluation and diagnostic tool for thyroid masses
Fine-needle aspiration biopsy (FNAB)
However, tissue diagnosis remains as the best predictor for surgical intervention. Majority of nodules sampled by
FNAD can be categorized as benign (65%), suspicious (20%), and malignant (5%).
management of thyroid Nodules in the suspicious category
SESAP is surgery siting 20-30% malignancy rate
SCORE says
a repeat biopsy or be subjected to other modes of characterization.
associated with production of calcitonin
Medullary thyroid carcinoma
parafollicular or C cells
The superior parathyroids are usually where give landmarks of nerve and thyroid gland where are ectopic sites
POSTERIOR and LATERAL to recurrent laryngeal nerve
1 cm above the junction of the nerve and the inferior thyroid artery
Embedded in fat along the posterior surface of the middle or upper portions of the thyroid lobes
Occasionally, a superior parathyroid may be found within the substance of the thyroid gland.
Other aberrant sites for the superior parathyroids include:
tracheoesophageal groove
retroesophageal space
posterior mediastinum
The inferior parathyroids are located
ANTERIOR and MEDIAL
to the recurrent laryngeal nerve
near the lower pole of the thyroid
or in the thyrothymic ligament
the most bioactive form of thyroid hormone.
T3
20% of T3 is secreted directly from the thyroid and
80% is derived by peripheral conversion from T4.
Renin is an enzyme secreted by
the juxtaglomerular cells of the kidney in response to decreased pressure in the renal afferent arterioles.
stimulation of Renin
Decreases in plasma sodium concentration sensed by osmoreceptors in the cells of the macula densa promote renin release as well.
Renin secretion is also stimulated by
hyperkalemia
HYPOnatriemia - which ultimately leads to release of angiotensin II that directly stimulates secretion of aldosterone.
inhibited by potassium depletion.
The major physiologic regulator of aldosterone secretion is
the renin–angiotensin system and angiotensin II directly stimulates secretion of aldosterone.
Somatostatin primary functions
Prolongs gastric emptying time.
decrease production of gastric acid
inhibit secretion of other peptide hormones including gastrin
Inhibits insulin secretion
most sensitive means to identify tumor recurrence in the thyroid bed or involvement of lymph nodes by metastatic disease during postoperative surveillance of patients with thyroid cancer.
Ultrasound!
roles of ultrasound for assessing thyroid mass
To preoperatively assess for evidence of tumor invasion into surrounding structures or for evidence of lymphadenopathy or abnormal-appearing lymph nodes!
To assess the thyroid gland and any nodules within it
As an adjunct to confirm needle placement during fine-needle aspiration of a thyroid nodule
Thyrotropin-releasing hormone is synthesized in the
hypothalamus
paraventricular nucleus of the hypothalamus.
It is a tropic hormone that stimulates the release of thyroid-stimulating hormone (TSH) and prolactin from the anterior pituitary gland.
management of indeterminate cytology on FNA of the thyroid nodule
“There is a 20% chance that an indeterminant specimen is actually a thyroid malignancy. “
Since there is no other test that would accurately determine the malignancy of the lesion, a thyroid lobectomy for diagnosis is the next most appropriate step in management.
If the lesion turned out to be a malignant thyroid neoplasm on final pathology, a reoperation for a completion thyroidectomy would be performed.
An alternative approach would be to offer a total thyroidectomy up front, which would eliminate the risk of reoperation but would require lifelong thyroid replacement therapy.
A thyroid lobectomy for diagnosis is considered the most appropriate management in this question scenario.
management of benign category FNA findings on thyroid nodule workup
Patients with a benign FNAB are recommended to undergo a repeat FNAB in 6 months.
If they continue to be asymptomatic, the nodule is unchanged, and the FNAB continues to be benign, they are recommended to continue with observation and yearly follow up.
external branch of the superior laryngeal nerve innervated
The cricothyroid muscle is innervated (CAREFUL-this is not cricopharyngeus)
functions to help maintain tension on the vocal cords.
arytenoids innervation and function
help form the intrinsic musculature of the larynx
innervated by the inferior laryngeal nerve,
which is the terminal branch of the recurrent laryngeal nerve.
intrinsic muscles of the larynx innervation
The are innervated by the recurrent laryngeal nerve.
Cricopharyngeus innervation and function
The cricopharyngeus is part of the inferior constrictor of the pharynx and is innervated by branches of the glossopharyngeal and vagus nerves
CAREFUL-this is not cricothyroid muscle innervated by the external branch the superior laryngeal nerve
Sternothyroid muscle location and innervation
one of the infrahyoid muscles of the neck,
all of which are innervated by upper cervical nerve fibers through the ansa cervicalis.
necessary for the induction of phenylethanolamine-N-methyltransferase activity, which catalyzes the conversion of norepinephrine to epinephrine.
Cortisol.
Catechol-o-methyl transferase (COMT)
the enzyme principally responsible for metabolism of the circulating catecholamines.
Catecholamine synthesis begins with
hepatic synthesis of tyrosine from phenylalanine and dietary sources.
most common cause of hypocalcemia after total thyroidectomy
Operative injury or excision of the parathyroid glands!!
The cause of the hypocalcemia is usually temporary, reversible ischemia of the parathyroid tissue, and hypocalcemia provides the maximum stimulus for the secretion of parathyroid hormone.
decision algorithm of treating a low serum calcium after total thyroidectomy
whether the patient has signs and symptoms of hypocalcemia,
such as paresthesias in the fingers, toes, or circumoral region; carpopedal spasm; agitation; laryngeal stridor; or a positive Chvostek’s sign.
If the patient is asymptomatic
and
calcium is >= 7.5 mg/dL,
simple monitoring of symptoms and calcium levels is the preferred method of management.
effective treatment for a symptomatic patient whose serum calcium is less than 7.5 mg/dL.
Intravenous or oral calcium
or
vitamin D
Oral calcium may be adequate for mild symptoms, but patients with severe symptoms such as carpal pedal spasm or laryngeal stridor 253should receive intravenous calcium, either as 10% calcium gluconate, which has a calcium content of 90 mg or 4.5 mEq, or 10% calcium chloride, which has a calcium content of 270 mg or 13.5 mEq.
VIP-secreting tumors are associated with
secretory diarrhea
and profound hypokalemia
Somatostatinoma are associated with
These include dyspepsia, mild diabetes mellitus, gallbladder disease, steatorrhea, and hypochlorhydria
Glucagonoma are associated with
frequently malignant pancreatic endocrine neoplasms characterized by elevated plasma glucagon levels that result in glucose intolerance and diabetes mellitus.
These patients also have a characteristic necrolytic migratory erythematous skin rash as well as weight loss and anemia.
Gastrinoma are associated with
Gastrinomas are associated with the development of virulent peptic ulcer disease and diarrhea (Zollinger-Ellison syndrome). Diabetes mellitus and skin rashes are not a part of this syndrome.
Pancreatic polypeptidoma are associated with
Pancreatic polypeptide secreting tumors of the pancreas are not associated with any identifiable clinical syndrome.
Excess iodide suppresses
both iodide transport and hormone synthesis
but does not affect peripheral conversion of T4 to T3.
Methimazole
Methimazole
member of the thionamide class of antithyroid drugs and inhibits thyroid hormone synthesis.
Dopamine effects on thyroid
inhibits pituitary secretion of TSH
Propranolol effects on thyroid
β-adrenergic receptor blocker,
controlling the peripheral manifestations of increased catecholamines sensitivity in patients with thyrotoxicosis.
It also has the effect of blocking peripheral conversion of T4 to T3, thereby slowing the metabolism rate of thyroid hormone.
Lithium effects on thyroid
Lithium inhibits the release of thyroid hormone
Verner-Morrison syndrome
is a secretory diarrhea, high levels of circulating VIP, and a pancreatic tumor.