Chapter 2 - Thyroid Flashcards
Disorder characterized by defective organification of iodine, goiter and sensorineural deafness
Pendred syndrome
What are the 5 factors that alter thyroid function in pregnancy?
1) Inc HCG (stimulates TSH-r)
2) Inc TBG (via estrogen)
3) altered immune system
4) Inc thyroid hormone metabolism (placenta)
5) Inc urinary iodide excretion
What hormones can suppress TSH secretions?
Dopamine
Glucocorticoids
Somatostatin
The most useful physiologic marker of thyroid hormone action?
TSH
Most common cause of diffuse nontoxic goiter worldwide?
Iodine deficiency
Most common malignancy of the endocrine system?
Thyroid carcinoma
Well differentiated thyroid ca
Papillary
Follicular
Undifferentiated thyroid ca
Anaplastic
What is the marker used in surveillance for:
A) Papillary and follicular Ca
B) Medullary Ca
A) Thyroglobulin
B) Calcitonin
Most common type of thyroid cancer?
Papillary Ca
Pathology: psammoma bodies, orphan annie nuclei
Spread: lymphatic, capsule invasion
What are the poor prognostic features of follicular thyroid ca?
1) Distant mets
2) >50 yo
3) >4cm size
4) Hurthle cell histology
5) Marked vascular invasion
Goal TSH level prior to starting RAI?
> 25 mIu/L
In hypothyroidism, after determining elevated TSH levels, the next step is to…?
Measure unbound T4
Elevated TSH, normal T4 but with present TPO antibodies and symptoms–do we treat with T4?
Yes
If TPO antibodies are negative and no symptoms, subject the patient to annual follow up
TRUE OR FALSE
Primary hypothyroidism is defined as elevated TSH, decreased T4
True
Present TPO antibodies determine an autoimmune cause and should be treated with T4
TRUE OR FALSE
In patients with normal TSH levels, low unbound T4, it would be prudent to rule out drug effects, sick euthyroid syndrome and evaluate for anterior pituitary disease
True
In evaluating thyroid nodules, the next step after receiving a NORMAL or ELEVATED TSH is?
Ultrasound
FNAB
Non diagnostic–repeat FNAB–if still non-diagnostic, close ff up or surgery
Malignant–pre op UTZ then surgery
In evaluating thyroid nodules, the next step after receiving a DECREASED TSH is?
Radionuclide scanning
Nonfunctioning nodule–UTZ
Hyperfunctioning nodule–manage as hyperthyroid
What is the protein precursor of thyroid hormones?
Thyroglobulin
Major positive regulator of TSH
TRH
What is the recommended average daily intake of iodine for specific populations?
Adults: 150-250mg/day
Children: 90-120mg/day
Pregnant/Lactating: 250mg/day
Most common cause of neonatal hypothyroidism?
Thyroid gland dysgenesis
Serum thyroglobulin levels are increased in all types of thyrotoxicosis except in where?
Thyrotoxicosis factitia
Autoantibodies that stimulate TSH-R in Graves disease?
TSI
Increased antibodies in autoimmune thyroid disease?
TPO
Effect of estrogen on:
A) TBG
B) Free hormones level
A) Inc TBG
B) Normal (Total hormones are elevated)
Sign illicited when arms are raised and it causes venous neck distention and difficulty breathing?
Common in retrosternal goiters.
Pemberton’s sign
Method of choice to determine thyroid size accurately
Ultrasound
Insidious painless goiter with symptoms due to compression?
Riedel’s thyroiditis
Treatment of subacute thyroiditis
Aspirin 600mg q4-q6
NSAIDS
Prednisone 40-60mg
Treatment of thyroid storm
PTU 500-1000mg loading then 250mg q4
SSKI 5 drops q6
Propranolol 60-80mg q4
Hydrocortisone 300mg IV bolus then 100mg q8
Hormone pattern in sick euthyroid syndrome
Low total and unbound T3
Normal T4 and TSH
Due to impaired T4 to T3 conversion
What are the 2 major forms of amiodarone induced thyrotoxicosis?
Type I - with underlying thyroid abnormality with excessive thyroid hormone synthesis (Jod-Basedow phenomenon)
Type II - no underlying thyroid abnormality; drug induced lysosomal activation leading to destructive thyroiditis with histiocyte accumulation
Phenomenon when excess iodide transiently inhibits thyroid iodide organification?
Wolff-Chaikoff effect
Dosing if methimazole and PTU?
Methimazole 10-20mg q8-12
PTU 100-200mg q6-8
Condition in the elderly wherein thyrotoxicosis may be subtle or masked?
Apathetic thyrotoxicosis
Most common cause of thyrotoxicosis?
Grave’s disease
Difference between thyrotoxicosis and hyperthyroidism?
Thyrotoxicosis - state of hormone excess
Hyperthyroidism - result of excessive thyroid function
Daily replacement dose of levothyroxine?
1.6
Dose of levothyroxine in starting treatment for subclinical hypothyroidism?
35-50 microgram/cl
Goal is to normalize TSH
Pathophysiology of myxedema in hypothyroidism
Increased dermal glycosaminoglycan content traps water
Disease wherein there is a marked lymphocytic infiltration of the thyroid with germinal center formation, atrophy of the follicles?
Hashimoto’s thyroiditis
