Thyroid Week 6 Flashcards
single best test for thyroid
TSH since the vast majority of cases of thyroid dysfunction are due to primary thyroid disease, to which the pituitary gland responds with predictable changes in TSH secretion
How do you interpret the serum TSH level?
if TSH is elevated, the patient almost always has primary hypothyroidism; when the TSH is low, the patient usually has primary hyperthyroidism
what labs change first if problem with the thyroid
Abnormal serum TSH values reflect mild thyroid dysfunction long before serum T 4 and T 3 levels are outside their reference ranges. Exceptions to these rules occur in patients who have pituitary-hypothalamic disorders or non-thyroidal illnesses. Measurement of serum free T 4 should be performed whenever the TSH level is high
why do we give thyroid replacement.
either replacement therapy for hypothyroidism or suppression therapy (lower than normal) for thyroid cancer
Free T 4 and T 3 assays determine what?
the amounts of unbound, bioactive thyroid hormones in the circulation
T4 aka
thyroxine, made by thyroid
T3 aka
triiodothyonine, made by thyroid
Serum free thyroxine (T 4 ) should be measured in ?
all patients whose TSH is elevatedand serum free T 4
serum free T 4 and total triiodothyronine (T 3 ) or free T 3
measured in patients whose TSH is suppressed
Anti- TPO (thyroid peroxidase) antibodies are the most accurate test to establish a diagnosis of ?
chronic lymphocytic thyroiditis (Hashimoto’s disease)
Serum thyroglobulin (TG) is useful for monitoring ?
- for recurrence of differentiated thyroid cancer and
- for assisting in the diagnosis of destructive thyroiditis
Radioactive iodine uptake (RAIU) is used primarily to ?
determine whether patients with thyrotoxicosis have a high-RAIU or low-RAIU disorder
A thyroid scan is used mainly to ?
distinguish among the three most common types of high-RAIU thyrotoxicosis: Graves ’ disease, toxic multinodular goiter, and a solitary toxic adenoma
most common world wide cause of hypothryoidism
iodine deficiency, need iodine to make T3 (poorer countries) but in developed countries- Hashimoto’s
The three most common causes of hyperthyroidism are
Graves’ disease, toxic multinodular goiter, and toxic adenoma
Thyrotoxicosis is the general term for what?
the presence of increased levels of thyroxine (T 4 ), triiodothyronine (T 3 ), or both, from any cause
whereas, hyperthyroidism refers to
causes of thyrotoxicosis in which the thyroid is actively overproducing thyroid hormone
Subclinical thyrotoxicosis is defined as ?
low serum TSH level with normal free T 4 and T 3
What is Graves’ disease ?
an autoimmune disorder in which activating autoantibodies directed against the TSH receptor result in continuous stimulation of thyroid hormone production and secretion as well as thyroid growth (goiter)
Extrathyroidal manifestations of Graves’ disease include what?
ophthalmopathy (proptosis, periorbital edema, extraocular muscle dysfunction, and optic neuropathy), dermopathy (pretibial myxedema), and thyroid acropachy (digital clubbing and edema)
what is a toxic multinodular goiter?
TMNG generally arises in the setting of a long-standing multinodular goiter in which certain individual nodules have developed autonomous function and secrete thyroid hormone independent of stimulation by TSH
What are autonomously functioning thyroid nodules?
AFTNs, or toxic adenomas, are benign tumors that have either constitutive activation of the TSH receptor or its signal-transduction apparatus. These tumors frequently produce subclinical thyrotoxicosis and have a predilection for spontaneous hemorrhage.
What is the Jod-Basedow phenomenon?
The Jod-Basedow phenomenon is iodine-induced thyrotoxicosis following exposure to large quantities of iodine (typically in iodinated radiographic contrast agents for CT or angiography, but also with the antiarrhythmic drug amiodarone)
TRH- thyroid releasing hormone made where?
hypothalamus. TRH goes to pituitary to tell the pituitary to make TSH thyroid stimulating hormone
