Thyroid Flashcards
Iodide is absorbed in the ____
Small intestine
Iodide is converted to organic iodine by ____
Peroxidase
The ____ (in thyroglobulin) are iodinated at one or two sites and then coupled to form the hormones T3 and T4
Tyrosines
____, a glycoprotein containing T3 and T4 within its matrix, is taken up as colloid droplets by the thyroid cells
Thyroglobulin
____ cleave T3 and T4 from thyroglobulin, resulting in the release of free T3 and T4
Lysosomes
Secretion of hormone from the thyroid depends on the amount of circulating ___
TSH
The level of TSH depends on the amount of ___ and on the level of free thyroid hormones in the circulation
TRH
Under normal conditions, only about __% of thyroid hormone secretion is T3
15%
80-85% of T4 and 70% of T3 are bound to this serum protein in the blood
TBG
What serum protein is bound to about 30% of T3 (5% of T4)
Albumin (TBA)
Only about __% of circulating T3 is produced by the thyroid
15%
About __% of daily T3 production takes place by conversion of free T4 to T3
80%
Protein-bound thyroid hormone is metabolically ____
Inert (inactive)
____ increases the rate of energy exchange and oxygen consumption by all body tissues
Thyroid hormone
Thyroid hormone stimulates the synthesis of ___ in virtually every body tissue
Protein
PBI stands for
Protein Bound Iodine
PBI is ___ in patients w/hyperthyroidism and ____ in patients w/hypothyroidism
Increased, decreased
A common reason for a false increase in PBI?
Pregnancy (or oral contraceptives)
Greater than normal levels of total T4 (thyroxine) indicate a ____ state, while decreased levels indicate the opposite
Hyperthyroid
Actual name for T3?
Triiodothyronine
Levels of carrier proteins (such as TBG) are concomitantly measured by T3 ____ studies (along with the usual Total T4 test)
Resin uptake
Possible critical value of total T4 in newborns?
<7.0 micrograms/dL
Critical values of total T4 for adults? (Both low and high)
<2.0 micrograms/dL (Myxedema coma possible)
>20 “ “ (thyroid storm possible)
Hypothyroidism in infants
Cretinism
Hypothyroidism in adults
Myxedema
Most common cause of hyperthyroidism
Grave’s disease
Most common cause of hypothyroidism
Hashimoto’s thyroiditis
Drug that decreases TBG
Steroid
Enlarged thyroid gland
Goiter
Hyperthyroidism in adults
Thyrotoxicosis
Hypothyroidism in a child
Juvenile
This test requires the antibody to T4
T4 by radioimmunoassay (RIA)
First thyroid test used
PBI
The sensitivity of T4 assay is approximately __% for hyperthyroidism and __% for hypothyroidism
95%, 92%
This test is one of the best for thyroid function and most accurately reflects thyroid status
Free Thyroxine Assay
This test measures the capacity of TBG to bind (“take up”) labeled T3 at unsaturated T4 sites
T3 Uptake Test (T3U)
In the T3 uptake test, high levels of uptake of 131 I-T3 by the resin (meaning low amounts were taken up by the open TBG sites) is indicative of ____thyroidism
Hyper
Another way to say normal thyroid
Euthyroid
This test is measured by multiplying the Total T4 result by the T3 uptake result. It was developed to correct the T4 assay for effects of thyroxine-binding protein alterations (i.e. increased/decreased TBG)
Free Thyroxine Index (FTI)
This test measures total serum T3 directly by using anti-T3 antibody. It is used to detect T3 Thyrotoxicosis.
T3 by RIA (T3 assay)
The ___ reflex is a good measure for tissue utilization of thyroxine (T4)
Achilles tendon
This measurement is inversely proportional to thyroid status
Cholesterol
The ___ concentration aids in differentiating primary from secondary hypothyroidism.
TSH (Thyroid Stimulating Hormone)
Pituitary TSH secretion is stimulated by hypothalamic ____ hormone
Thyroid-releasing (TRH)
An elevation in TRH and TSH would indicate a patient with ____ hypothyroidism
Primary (T3 and T4 are low, leading to increased stimulation of TRH and therefore TSH)
A patient with secondary hypothyroidism would have __ levels of TRH and TSH
Low
Decreased levels of TSH could indicate what two things?
- Secondary hypothyroidism
2. Hyperthyroidism
What thyroid test is considered a good SCREENING test?
TSH test
The American Thyroid Association recommends that adults be screened for thyroid dysfunction by measurement of TSH beginning at age ___ and every 5 years thereafter.
35
Antithyroglobulin antibody and antithyroid microsomal antibody would both be increased in patient’s w/this hypothyroid disease
Hashimoto’s thyroiditis
Treatment for patients w/primary hypothyroidism (cretinism, juvenile hypothyroidism, myxedema)
Thyroid hormone for life (synthetic thyroxine)
ALP is ____ in hypothyroidism
Decreased
Common name for Toxic diffuse goiter
Grave’s disease
Common name for Toxic nodular goiter
Plummer’s disease
The most common cause of goiter worldwide
Iodine deficiency
