Thyroid Flashcards
Best initial test of thyroid function…
TSH
What is tightly regulated by serum levels of T3/T4?
TSH (inverse relationship)
FT4 is used to evaluate an abnormal…
TSH
is free T4 or total t4 more diagnostically relevant?
FT4
T4 is converted to T3 where
liver mostly
Which Abs are mostly found in hypothyroidism (hashimoto’s)?
TPO Ab
(thyroid peroxidase)
TgAb
(thyroglobulin)
Which Abs are most often found in hyperthyroidism (Graves)?
TRAb
thyrotropic receptor
This is a functional study used to evaluate a suppressed TSH/hyperthyroid…
radioactive iodine uptake
This is a non-invasive imaging that can assess structure of thyroid gland tissue
US
US is helpful in assessing…
nodules
This is the most accurate, reliable, cost-effective test to dx thyroid ca
fine needle aspiration
Decreased TSH
Elevated FT4/T3…
Hyperthyroidism
4 endogenous causes of hyperthyroidism…
graves
toxic multinodular goiter
toxic adenoma
thyroiditis
Exogenous hyperthyroid ism is…
iatrogenic in nature
What type of hyperthyroidism?
Decreased TSH
Increased FT4
Increased T3
Graves (Most Common Cause)
What type of hyperthyroidism?
Decreased TSH
Normal FT4/T3
Sublinical hyperthyroidism
What type of hyperthyroidism?
Decreased TSH
Normal FT4
Increased T3
T3 toxicosis
What causes the following result of radioactive iodine uptake…
diffuse high
de-novo synth of hormone
What causes the following result of radioactive iodine uptake…
diffuse low
inflammation/destruction
extrathyroid source of hormone (factitious thyrotoxicosis)
radioactive iodine uptake in Grave’s disease…
diffuse
What causes the following result of radioactive iodine uptake…
increased irregular uptake
hyperfunctioning “hot” nodules
are hot nodules usually malignant?
no
What causes the following result of radioactive iodine uptake…
decreased irregular uptake
hypofunctioning “cold” nodules
Are cold nodules malignant?
yes, consider FNA
Subacute thyroididits RAI Uptake result…what other tests?
decreased uptake, ESR/CRP
Toxic MNG RAI Uptake Result… what other tests?
Irregular, US
Toxic adenoma RAI Uptake result… what other tests?
irregular, US
exogenous etiology of hyperthyroidism RAI Uptake result… what other tests?
decreased uptake, serum Tg
A patient presents w/ hypothyroid sxs and:
+ TPO Ab, TgAb
primary hypothyroidism (hashimoto thyroiditis)
A patient presents w/ hypothyroid sxs and:
low TSH and low FT4
Central hypothyroidism
Secondary central hypothyroidism is a disease of the…
pituitary
tertiary central hypothyroidism is a disease of the…
hypothalamus
How do you assess central hypothyroidism?
pituitary MRI
What four medications may cause iatrogenic hypothyroidism?
lithium
amiodarone
iodine drugs
contrast agents
What would you be suspicious of with the following labs?
increased TSH
decreased FT4
normal/decreased T3
Primary hypothyroidism (MC hashimotos thyroiditis)
What would you be suspicious of with the following labs?
increased TSH
Normal FT4/T3
subclinical hypothyroidism
What would you be suspicious of with the following labs?
normal/low TSH
subnormal FT4
normal/low T3
central hypothyroidism
How do you treat hypothyroidism?
levothyroxine replacement
What is dosing based on for levothyroxine?
weight-based
When should levothyroxine be taken?
empty stomach 1 hour before breakfast
First line test and imaging for thyroid nodule…
TSH and US
Is thyroid CA common? Are thyroid nodules common?
CA: no
Nodules: yes
If a patient has a nodule and subnormal TSH, what is the next step?
RAI uptake scan
What test should be ordered if there is a hot nodule?
FT4/T3
If hot nodule and sublinical hyperthyroidism, what is the next move?
observe
If hot nodule and overt hyperthyroidism, what is the next step?
tx
If you have a cold nodule, what is the next step?
FNA
If you have a nodule and normal/elevated TSH, what should be done next?
check TPO abs, consider FNA
Low TSH/High FT4…
primary hyperthyroidism
High TSH/Low FT4…
primary hypothyroidism
Low TSH, low FT4, consider…
pituitary MRI
tetany, chvostek sign, trousseau sign, prlonged QT are signs of…
hypoPTH
The following labs are concerning for…
Decreased PTH
Decreased Ca
Increased Phosphate
hypoPTH
Common cause of hypoPTH…
post-surg/irradiation
Bones, stones, moans, groans…
primary hyperPTH
MC cause of primary hyperPTH…
parathyroid adenoma
A patient with the following labs is concerning for…
increased PTH
increased Ca
Decreased PO4
primary hyperPTH
how do you treat hypoPTH?
Ca, vit D
How do you tx primary hyperPTH?
bisphosphonates, parathyroidectomy
A patient with the following labs is concerning for…
Increased PTH
decreased Ca
Incrased PO4
secondary hyperPTH
What is the MC cause of secondary hyperPTH?
CKD
How do you tx secondary hyperPTH?
renal mgmt
nodule protocol…
TSH/US
Subnormal TSH = RIU
Cold = FNA, Hot = FT4, T3
Hot w/ overt hyper = tx, hot w/ sublinical hyper = observe
