378 Thyroid Nodules Flashcards
Weight of thyroid gland
12-20 grams
Drugs that prevent the peripheral conversion of thyroid hormones
PTU
Propranolol
Glucocorticoids
Amiodarone
Half life of T3
2 days
True or false. Right lobe of thyroid is larger than the left
True
Percentage of T4 coming from the thyroid
100%
Percentage of T3 coming from thyroid
20%
RAI contraindication
Pregnancy
Breastfeeding
When does thyroid synthesis begin
11 weeks gestation
Where does the thyroid gland develop
Floor of the primitive pharynx during 3rd week of gestation
Failure of the thyroid gland to migrate in the neck and is found at the base of the tongue
Lingual thyroid
Gives rise to calcitonin
Thyroid medullary C cells
Where are the C cells located
Upper 1/3
Lower 2/3
Of thyroid gland
Orchestrate thyroid gland development
Homeobox-8 (PAX 8)
Where are the follicular cells of the thyroid located
Basolateral surface
Subunit of TSH common to other hormones and the subunit unique to TSH
Alpha unit similar to other glycoprotein hormones
Beta unit unique to TSH
What hormones are similar to the TSH alpha unit
LH
FSH
hCG
Suppresses TSH
Dopamine
Glucocorticoids
Somastostatin
Major positive regulator of TSH
TRH
Critical first step in thyroid hormone synthesis
Iodine uptake
Mediated iodide uptake, expressed in the basolateral membrane of the follicular cells
NIS (Sodium iodide symporter)
Low levels of NIS is expressed in which organs
Salivary glands
Lactating breast
Placenta
Iodine transporter in the basolateral surface? On the apical surface?
Basolateral: NIS
Apical: pendrin
Disorder characterized by defective organification of iodine, Goiter had sensorinueral deafness
Pendred syndrome
Characterized by mental and growth retardation in iodine deficient regions
Cretinism
Concomitant deficiency in cretinism that contribute to neurologic manifestation
Selenium deficiency
Recommended average daily intake of iodine
150-250 ug/day
Disorders of thyroid hormone synthesis is due to what mutations
Recessive mutations of TPO or Tg
Excess iodide transiently inhibits thyroid iodide organification
Wolf chaikoff phenomenon
Types of deiodinases. Where are they found
Type I: low affinity, thyroid, liver and kidneys
Type II: strong affinity, pituitary, brain, brown fat, thyroid
Type III: most import source of rT3
Caused by self administration of thyroid hormone
Thyrotoxicosis factitia
Increased in all type of Thyrotoxicosis except Thyrotoxicosis factitia
Serum Tg
Main role of Tg measurement
Follow up thyroid cancer
Hot vs cold nodule on thyroid scintigraphy
Hot: never malignant
Cold: likely malignant
Most common type of thyroid cancer
Papillary thyroid cancer
Characteristic cytologic features of PTC
psammoma bodes, cleaved nuclei with orphan annie appearance
Where does follicular thyroid cancer spread?
hematogenously to bone, lung, and CNS
Main stay of thyroid cancer treatment as most tumors are TSH responsive
levothyroxine suppression
Aggressive thyroid cancer and patient often die 6 months of diagnosis
anaplastic thyrpid cancer
True or false. lymphoma in the thyroid gland often arises in the background of Hashimotos thyroiditis
True
Most common type of thyroid lymphoma
Diffuse large cell lymphoma
refers to an enlarged thyroid gland
goiter
True or false. Graves’ disease and Hashimoto’s thyroidism are also associated with goiter
True.
pathogenesis of goiter in Grave’s disease
TRH mediated effects of thryoid stimulating immunoglobulin
pathogenesis of goiter in Hashimoto’s thyroidism
goitrous form pccurs because of acquired defects in hormone synthesis, leading to elevated levels of TSH and its consequent growth effects
Diffuse enlargement of the thyroid in the absence of nodules and hyperthyroidism
diffuse nontoxic goiter
other name of diffuse nontoxic goiter
simple goiter, colloid goiter
most common cause of diffuse goiter worldwide
iodine deficiency
thyroid enlargement in teenagers
juvenile goiter
true or false. In iodine deficient areas, thyroid enlargement reflects a compensatory effort to trap iodine and produce sufficient hormone when hormone synthesis is relatively inefficient
True.
what is the action of iodine to thyroid growth
direct actions on thyroid vasculature and indirectly affect growth through vasoactive substances such as endothelin and nitric oxide
abnormal thyroid volume on ultrasound
more than 30 ml
refers to the facial and neck congestion due to jugular venous obstruction when the arms are raised above the head
Compression exceed 70% of the tracheal diameter
manuever that draw the thyroid to the thoracic inlet
Pembertons sign
associated with Pemberton signs
substernal goiter
laboratory findings that support iodine deficiency
low urinary iodine levels less than 50 ug/L
True or false. Iodine replacement induces variable regression of goiter in iodine deficiency depending on the duration and degree of hyperplasia
True.
conditions where surgery is indicated in diffuse goiter
tracheal compression or obstruction of the thoracic inlet
True or false. Surgery is rarely indicated for diffuse goiter
True.
True or false. TSH is play an permissive or contributory role in nontoxic multinodular goiter
True.
True or false. Most patients with nontonic multinodular goiter are asymptomatic and euthyroid
True.
What leads to hoarseness of voice in patient with goiter
laryngeal nerve involvement
True or false. Pain and hoarseness of voice in goiter suggests malignancy
True.
At what level can tracheal compression lead to significant airway compromise
Compression exceed 70% of the tracheal diameter
sonographic features assocaited with thyroid cancer
hypoechoic compared with surrounding thyroid, marked hypoechogenicity, microcalcifications, irregular microlobulated margins, solid consistency, taller than wide shape on transverse view
characterized by enhanced thyroid production by autonomous nodules
Jod Baselow effect