Thyroid Flashcards
(44 cards)
What hormones does dopamine inhibit?
Prolactin and TRH and TSH.
What increases thyroxine-binding globulin (TBG)?
Estrogen increases (e.g. OCP, pregnancy)
Hepatitis
Opioids
Hereditary
What decreases thyroxine-binding globulin (TBG)?
Androgens Glucocorticoids Nephritic syndrome Cirrhosis Acromegaly Antiepileptics Hereditary
In which situation do we want to see if reverse T3 is high?
Sick euthyroid syndrome
It’s an inactive molecule
Antithyroid peroxidase antibodies (TPO Ab) are seen in which thyroid conditions?
Hashimotos (high titre)
Painless thyroiditis
Graves’ disease (low titre)
In which conditions will thyroglobulin be increased above normal?
Goiter
Hyperthyroidism
Thyroiditis
In which conditions is thyroglobulin decreased from normal?
Factitious ingestion of thyroid hormone
What do we use thyroglobulin for clinically?
Detecting thyroid cancer recurrence, relapse or metastasis . Need to measure antibodies to thyroglobulin as well to help interpret.
It is a tumor marker after total thyroidectomy and radioiodine therapy
Which conditions will there be increased uptake on a radioactive iodine uptake scan?
Used to differentiate causes of hyperthyroidism.
Increased in:
Graves (homogenous)
Multinodular goiter (hererogenous)
Hot/toxic nodule (focal uptake, suppression of rest of gland)
In what conditions is there no uptake on RAIU but there is clinical hyperthyroidism?
Thyroiditis (subacute painful aka de Quervain’s or painless)
Exogenous thyroid hormone
Recent iodine load
Struma ovarii (rare ovarian tumor/teratoma comprised of >50% thyroid tissue so thyroid gland is less active/suppressed)
Antithyroid drugs
Primary hypothyroidism comprises what % of hypothyroid cases?
> 90%
List the causes of primary hypothyroidism
Goitrous:
- Hashimoto’s thyroiditis
- Iodine deficiency
- Lithium
- Amiodarone
Non-goitrous:
- surgical destruction
- after RAI
- after radiation therapy
- Amiodarone
What % of patients with Hashimoto’s thyroiditis have anti-TPO
> 90%
What menstrual abnormalities occur in hypothyroidism?
Menorrhagia
What type of hypertension does hypothyroidism cause?
Diastolic hypertension
What are the characteristics of a myxedema coma?
Hypothermia (<35 degrees)
Hypotension
Hypoglycaemia
Hypoventilation and hypercarbia and hypoxemia
Bradycardia
Mental status changes like coma (lethargy, obtundation, stupor, seizures)
Hyponatremia
GI findings (abdo pain/constipation, decreased gut motility, paralytic ileus)
EKG changes (long QT, low voltage, bundle branch blocks, other heart blocks, or other ST changes)
Pericardial or pleural effusion
Pulmonary edema
Cardiomegaly
AKI
Has a precipitating factor usually like infection or neurological illness or cardiopulmonary issue
What meds or nutrients decrease synthroid absorption?
Iron Calcium Cholestyramine Sucralfate PPI
What medications accelerate thyroxine catabolism?
Phenytoin
Phenobarbital
If giving someone estrogen or if someone is pregnant and hypothyroid, how do you tell them to increase their thyroid hormone due to increased need?
J
Why does pregnancy increase synthroid need and by how much (%)?
30-50% increase Due to combination of: -estrogen stimulating TBG so less free hormone -increased volume of distribution -T4 cleared by placental deiodinases -HCG competitively binds at TSH receptor
What is the goal TSH during pregnancy?
Lower targets
<2.5 first trimester
<3.5 thereafter
How often do you need to check TSH in pregnancy?
Every 4-6 weeks in first and second trimester and then no need to check in third trimester
When does a fetus begin thyroid function
20 weeks and above
How do you treat myxedema coma?
Load 5-8 microgram/kg IV levothyroxine (T4) then 50-100 micrograms daily because peripheral conversion is impaired.
Uptodate states 200-400 mcg bolus then 50-100 daily. It should raise levels by 2-4 McG/dL. Choose lower end of dosing range for those who are at higher risk for cardiac complications (MI, arrhythmia) and older patients.
Also give T3 (some people only do either T3 or T4 alone and some do combination) because greater biologic activity and faster onset.
IV T3 5-20 mcg then 2.5-10 q8h
ALSO give empiric stress steroids because decreased adrenal reserves in severe illness but also because you cannot exclude underlying adrenal insufficiency (primary or secondary)
