Thyroid Gland Flashcards
What type of transport is used to transport iodide into the thyroid gland cell?
Active transport
What occurs once iodide is actively transported into cells?
Iodide is oxidised to iodine
Monoiodotyrosine (MIT) and diodotyrosine (DIT) together make up which form of thyroid hormone?
Triiodothyronine (T3)
Two diodotyrosines (DIT) together make up which form of thyroglobulin?
Thyroxine (T4)
How much of T3 in the plasma is secreted by the thyroid?
20%
What molecules act on the pituitary gland to inhibit thyroid hormone secretion?
Corticosteroids, dopamine.
List the effects of T3 and T4 on the liver.
Increased gluconeogenesis, glycogenolysis and blood glucose.
List the effects of T3 and T4 on the GI tract.
Increased CHO absorption
List the effects of T3 and T4 on the muscles.
Increased protein synthesis and even more increased protein degradation.
List the effects of T3 and T4 on adipose tissue.
Increased lipogenesis and even more increased lipolysis.
What factors increase TRH secretion?
Cold, acute psychosis, circadian rhythm, decreased T3 and T4..
What factors decreases TRH secretion?
Severe stress, increased T3 and T4.
What are the secretion patterns of T3 and T4 like?
Pulsatile for T4 (peaks in morning) and diurnal for T3.
What happens once T4 and T3 enter the cell?
All T4 is converted to T3 and T3 enters the nucleus.
What is the effect of thyroid hormone on growth?
Growth formation, bone maturation.
What is the effect of thyroid hormone on the CNS?
Maturation of the CNS
What is the effect of thyroid hormone on BMR?
Increase sodium-potassium pump activity, oxygen consumption, heat production and BMR.
What is the effect of thyroid hormone on metabolism?
Increased glucose absorption, glycogenolysis, gluconeogenesis, lipolysis, net protein catabolism.
What is the effect of thyroid hormone on the CVS?
Increased cardiac output through potentiation of the effects of catecholdamines.
Why is serum TSH measured?
To determine whether there is a primary or secondary thyroid defect.
In immunoassays are total TSH or free TSH of clinical significance?
Free TSH as free TSH has biological activity.
What are radioiodine studies used for?
To determine the thyroid areas with increased or decreased function.
What is indicative of primary hyperthyroidism?
Low TSH and high T3/T4.
What is indicative of secondary hyperthyroidism?
High TSH and high T3/T4.
What is indicative of primary hypothyroidism?
High TSH and low T3/T4.
What is indicative of secondary hypothyroidism?
Low TSH and low T3/T4.
In radioiodine studies what are cold and hot nodes?
Cold nodes- low activity
Hot nodes- high activity.
What autoimmune disease causes hypothyroidism?
Hashimotos disease- production of antibodies against thyroglobulin.
What autoimmune disease causes hyperthyroidism?
Graves disease- production of molecules that mimic T3/T4.
