Thyroid Flashcards
Thyroid hormones
Thyroxine (T4)
Triiodothyronine (T3)
T4
Thyroxine
T3
Triiodothyronine
Functions (general) of thyroid hormones
metabolic homeostasis
- affect every tissue
- protein, lipid, carb metabolism
- cell differentiation, growth, development
NIS
sodium iodide symporter
Thyroid regulation
- transport proteins
- maintain serum levels of thyroglobulin
- peripheral metabolism by deiodinases
- metabolism of iodine
- hypothalamic-pituitary control
TSH
thyroid stimulating hormone
-stimulates NIS to accumulate iodine
deiodinases
converts T4-T3-T2
NIS locations
thyroid, salivary glands, placenta, brain, lactating breast
T4 potency
1
T4 protein bound
10-20
T4 half life
5-7 days
T4 amount secreted by thyroid
80-100 micrograms/day
T3 potency
10
T3 protein bound
1
T3 half life
<24 hours
T3 secreted by thyroid
6-10 micrograms / day
TSH
Thyroid stimulating hormone
- controled by T4 and T3 levels on pituitary
- levels equate to hypo/hyper
- euthyroid = normal
Thyroid condition prevelance
hypothyroidism more prevalent than hyper
Hypothyroidism symptoms
fatigue weight gain cold intolerance skin dryness hair dryness depression dementia cramps edema bradycardia constipation
Hyperthyroidism
fatigue weight loss heat intolerance hyperhydrosis nervousness insomnia tremor weakness menstrual irregularities palpitations hyperdefecation
Fetal hypothyroidism
low birth weight
congenital cretinism
congenital cretinism
growth failure
mental retardation
neurodevelopmental delays
iodine levels for cretinism
<20-25 micrograms /day
most common malignant tumor of endocrine system
thyroid cancer
Thyroid cancer presentation
- painless lump
- normal function
- routine exam
- slow growth
Thyroid cancer types
Differentiated
Undifferentiated
Differentiated thyroid cancers
papillary (PTC) - 75-85 %
follicular (FTC) 5-15 %
Undifferentiated thyroid cancers
Anaplastic Thyroid carcinoma (ATC)
Medullary thyroid carcinoma (MTC)
Carcinoma compared to benign nodules
Carcinomas only 5%
PTC
Females 3x more likely and in midlife
graves disease
most common hyperthyroidism
thyroid cancer latency
5-7 years
Why does it appear thyroid cancer incidence has increased
surveillance bias
iodine uptake depends on
- percent of administers that enters thyroid
- size of thyroid
- bio half life
percent administered that enters thyroid depends on
- amount of stable iodine in diet
- age of patient
- gland level of function
