173. Thyroid basic physiology Flashcards
In biochemical thyroid function tests, displays antibodies to TPO
Hashimoto’s thyroiditis
Elevated TSH Decreased total or free T4
Hypothyroidism
Functional unit of the thyroid
Follicle
Low iodine –> low thyroid hormones –> increased TSH –> increased thyroid size
Goiter
Elevated TSH Normal total or free T4
Subclinical hypothyroidism
GPCR that allows Iodine (I-) to enter the thyroid cells from the blood stream Regulated by TSH
NIS
Echo free center on US Smooth back wall Acoustic enhancement
Thyroid cyst
Severe mental retardation 2/2 insufficient hormone levels during intrauterine life and infancy
Cretinism (congenital iodine deficiency)
Modality of choice for evaluation of thyroid structure No functional information Diagnosis: - nodules - cysts - Hashimoto’s - Graves’ Can be used to guid fine-needle biopsy
US
Emits gamma and beta radiation Beta radiation destroys tissues Used to assess thyroid and whole body scan Used to treat Graves’, toxic adenomas, and thyroid cancer
131iodine scan
Enzymes that convert T4 into active T3 Occurs in the peripheral cells
5-Monodeiodinase DIO1 and DIO2
In biochemical thyroid function tests, this is a tumor marker for MTC
calcitonin
Decreased TSH Normal total or free T4
Subclinical hyperthyroidism
Still significant health problem for about 1/3 of the world population 20 million people mentally handicapped d/t this Most preventable cause of mental impairment
Iodine Deficiency Disorders (IDD)
Action is primarily mediated by nuclear receptors regulating gene transcription
Thyroid hormones
Uptake of iodine tracer can be quantified to obtain estimate of ___ Radioiodine uptake
metabolic function
Thyroid hormone receptors in the gut Non-steroid hormone receptor
TRbeta1
Enzyme that converts T4 into rT3 (not biologically active)
5-Monodeiodinase DIO3
Thyroid hormone receptors in the thyroid Non-steroid hormone receptor
TRbeta2
Emits gamma radiation to be used in thyroid scanning
99technetium scan
Damage tissue and are emitted in a 131iodine scan Used to treat hyperthyroidism
beta particles
Stimulates growth and function of thyroid follicular cells resulting in the production of T4 and T3
TSH
Most active thyroid hormone that does most of the work
T3
Autoimmune thyroid destruction
Hashimoto’s thyroiditis
Enzyme that forms iodine with thyroglobulin into T3/T4
TPO
Emits gamma radiation Used to assess thyroid function and whole body scan
123iodine scan
Decreased TSH Elevated total or free T4
Hyperthyroidism
In biochemical thyroid function tests, displays antibodies to TSH receptors
Graves’ Disease
Thyroid hormone receptors in the heart Non-steroid hormone receptor
TRalpha1 and 2
Hypoechoic signal, irregular borders, and microcalcifications on US point towards..
Thyroid cancer
The more thyroid tissue, the higher the ___ Detectable amounts = residual or recurrent thyroid cancer tissue Increase may only be detectable under conditions of high TSH
TG level
Transports thyroid hormones into peripheral cells from the bloodstream when they are free Can be mutated, esp. at the BBB leading to central hypothyroidism
Thyroid hormone transporter
Binding proteins of T4/T3 >99% of T4/T3 is protein bound
TBG (thyroid-binding globulin) > TTR > Albumin
Negative regulation of the hypothalamic-pituitary-thyroid axis is controlled by..
T3 Somatostatin Dopamine
~10% of normal individuals have these ~20% of pts w/ thyroid cancer have these Can interfere with the TG measurement Can be an indicator of residual or recurrent thyroid cancer tissue
Thyroglobulin Abs
In biochemical thyroid function tests, this is a tumor marker for PTC, FTC
thyroglobulin
Most common cause worldwide of thyroid disorders
Iodine deficiency
