Thyroid Gland Functions and Disease Flashcards
Peripheral conversion of T4 to T3 is done by what enzyme?
Deiodinase
Which deiodinase type is predominantly in the peripheral tissues?
Type 1
During fasting, would you expect more or less conversion of T4 to T3.
Less
What factors are associated with increase in conversion of T4 to T3
Obesity
cold exposure
hyperthyroid
What factors are associated with decrease in conversion of T4 to T3?
Pregnancy fasting beta blockers hepatic and renal failure aging hypothyroid
How many Na comes in with I- in the NIS?
2 Na.
What aa is the precursor for thyroglobulin?
Tyrosine
What what channel does I- go from the cell to the colloid?
Pendrin
Via what transport mechanism do TG-T3-T4 bound complex get inside the cell after TSH stimulation?
Pinocytosis inside a endosome.
NIS can be blocked by what drug?
Percholarate, thiocynate.
PTU is an effective treatment for hyperthyroidsim which works by blockig action of what enzyme?
peroxidase
High levels of I- inhibits organification and synthesis of thyroid hormones. this effect is known as
Walff-Chaikoff
Of the iodide that comes into the thyroid gland is stored in what form?
Stored iodinated as tyrosines of thyroglobulin inside the colloid of follicular lumen.
With iodine deficiency, how long can you go without showing signs of hypothyroidism?
2-3 months
Which thyroid hormone binding protein brings the thyroid hormone to the brain?
Transthyretin.
Thyroxine-binding protein (TBG) has a higher affinity for which thyroid hormone (T3 or T4?
T4
Describe the steps to T3 resin uptake test.
- Obtain TBG w/bound T4 from serum.
- Add unbound and labeled T3
- Incubate - Allow binding to take place
- Add Anti T3, or non specific resin which adsorbs T3.
- From solution, remove TBG w/bound T4 and labeled T3
- Precipitate the adsorbed T3
During hyperthyroidsim, what would be levels of T4 and T3 resin uptake (increased or decreased)
Both increased
During hypothyroidsim, what would be the levels of T4 and T3 resin uptake (increasd or decrease)
Both decreased
During High TBG levels, would be the levels of T4 and T3 resin Uptake?
T4 is increased
T3 resin uptake is decreased
During low TBG levels, what would be the level of T4, T3 resin uptake, increase or decrease.
decreased T4
increased T3 resin uptake
During hepatic failure, what would be the levels of T3 resin uptake and TBG?
TBG is decreased. T3 resin uptake increased
Druig pregnancy what would be the levels of TBG and T3 resin uptake
TBG is increased
T3 resin uptake is decreased.
DUring pregnancy, a person is said to be clinically euthyroid, why?
During pregnancy TBG levels increase and so bound T3 and T4 increases, and free ones decrease. And since free ones decreased, the body sense that as deficiency and so they make more T3 and T4.. So overlll total T3 and T4 increase, but the levels of free physiologically active T3 and T4 remains realtively normal (euthyroid)
What factors stimulate thyroid hormone secretion?
- TSH
- Pregnancy
- Thyroid-stimulating immunoglobulins
What factors inhibit thyroid hormone secretion?
- Iodide deficiency
- deiodinase deficiency
- Excessive iodide intake (Wolff-Chaikoff effect)
- percholorate, thiocyanate
Prophylthiouracil - Decreased TBG levels (e.g. liver disease)
Thyroid hormones stimulates production of new proteins in it’s target tissues/cells. What are some example of the types of proteins thyroid hormone would stimulate the production of?
- Na/K ATPase
-transport proteins
-B-adrenergice receptors
lysosomal enzymes
-protlytic protiens
-structural proteins
Thyroid hormone stimulates the production of what in cardiac muscle cells?
- myosin
- beta-adrenergic receptors
- Ca ATpase
In the liver and adipose tissue, thyroid hormones induce the synthesis of what types of enzymes?
Metabolic enzymes.
Name one thing, thyroid hormone does in each of these systems:
- Growth
- CNS
- BMR
- metabolism
- Cardiovascular
- Increase growth formation and bone maturation
- Maturation of CNS
- Increase Na/K Atpase; O2 consumption; heat production and BMR
- Increase glucose absorption, glycogenolysisi, gluconeogeneiss, lipolysis, protien synthesis and degradation (net catabolic)
- Increase CO
in response to thyroid hormone the increase in basal metabolic rate is mainly attributed to the increased activity of _
Na/K ATPase leading to increased O2 consumption and heat production
In hypothyroidism, how would the blood cholesterol concentration change? Increase or decrease?
Increase.
what hormone is required for the conversion of carotene to vitamin A
Thyroxine?
What cardiac receptors do thyroid hormone stimulate/inhibit
THyroid hormone has both chronotorpic and ionotropic effect on cardiac receptors. It will stimulate beta adrenergic receptors while inhibiting muscarinic receptors.
A new born baby presents with feeding problems, respiratory difficulty, tongue, curse facial features, growth retardation, mental retardation, jaundice, dry skin, hypotonia. what is the the likely diagnosis?
Cretinism
What causes the exophthalmos, and periorbital edema as seen in Graves disease?
Due to recognition by the anti-TSH receptor antibodies of a similar epitope within the orbital cells.
What three findings confirms graves disease?
- elevated serum free and total T4 and T3
- Clinical signs of goiter
- Ophthalmopathy
- Low TSH
- serum levels of TSI
Circulating levels of what proteins distinguishes Graves disease from adenoma of pituitary thyrotrophs?
TSI
A patient had blood drawn to diagnose his thyroid issues. the following were seen: decreased TSH, Increased T3/T4, and positive for TSI, and radioactive iodine uptake test showed increased uptake. What is the diagnosis?
Graves Disease
What disease is likely to be associated with the following finding? Increased TSH, decreased or normal T3/T4 and positive for antithyroid antibody.
Hashimoto
What disease is likely to be associated with the following findings: decreased TSH, decreased T3/T4, and negative for antithyroid antibody
Pituitary abnormality
