endocrinology lecture 2 Flashcards
where is the thyroid gland found? what connects it?
either side of the trachea
connected by isthmus
what is the thyroid gland organized into?
follicles
balls of follicular cells, single layer forms ball
what is found in the middle of a thyroid follicle?
colloid
fluid filled inner portion filled with proteins
the colloid fluid is made by __________
made by follicular cells
follicular cells regulate the production of which two iodine-containing hormones?
T3 and T4
thyroid hormones are ____ based hormones
lipid soluble, amine based hormones
why is a colloid storage mechanism needed in the thyroid?
prevents diffusion of the hormones out of the cells
______ stimulates the thyroid gland to take up iodine with sodium (Na+)
TSH
follicular cells also secrete __________, which has many tyrosine residues
thyroglobulin
what is iodine oxidized by? what happens after oxidation?
oxidized by THYROID PEROXIDASE
linked to thyroglobulin (on the tyrosine residues)
what molecules combine to form T3 and T4?
MITs and DITs
mono or di thyrotyrosine
thyroid hormone is stored in colloid attached to __________
thyroglobulin
what stimulates thyroid hormone release?
TSH (from pituitary gland)
droplets of thyroglobulin fuse with ______ and T3 & T4 are released
lysosomes
_______ of T4 is converted to T3 in the liver and kidneys
80%
thyroid hormone exerts a negative feedback effect on the secretion of ___ and ___
TRH and TSH
what are the forms of thyroid hormone receptors? what are they encoded by?
alpha and beta forms
encoded by 2 different genes
a dimerized receptor + TH will regulate ____________
gene transcription
how does TH stimulate cellular metabolism?
1) increase Na/K-ATPase activity
2) increase substrate availability
3) produces heat
t/f: Thyroid hormone can upregulate beta-adrenergic receptors
true
the effect of up regulating beta-adrenergic receptors leads to an increased sensitivity to ___________
catecholamines
NE and E
TH is important for neuron _______ and _______
growth and development
insufficient TH during fetal development causes ________
cretinism
what are the most common endocrine diseases?
diseases of the thyroid gland
both hypo-, and hyperthyroidism can lead to ______ development
goiter
what is the consequence of hyper- or hypothyroidism?
Thyroid hormone normally inhibits TSH & TRH
- too much, or too little, of TH will disrupt this balance
Hypothyroidism is most often caused by what?
a primary defect in the thyroid gland
T/F: 95% of the defects that cause hypothyroidism are due to a Iodine deficiency
True
what effect does a lack of thyroid hormone have on TRH and TSH?
causes an increase in TRH and TSH due to a lack of feedback inhibition
why does hypothyroidism cause a goiter?
unregulated TSH stimulation (due to lack of TH release)
what are the effects of cretinism? (fetal iodine deficiency)
short stature
mental retardation
besides iodine deficiency, what are the other defects leading to hypothyroidism?
A) autoimmune thyroiditis
B) damage or destruction of gland
C) dysfunction associated with other illness
what are the MILD symptoms/consequences of hypothyroidism?
- related to metabolic effects of TH
- sensitive to cold, slight weight gain
what are the MODERATE symptoms of hypothyroidism?
- enough of a deficiency to cause lack of catacholamine response
- fatigue, reduction in: blood flow, skin tone, GI & mental function
the SEVERE effects of hypothyroidism include _______ due to an accumulation of what?
myxedema (bloating of soft tissue)
accumulation of glycosaminoglycans (GAGs) in ECF
t/f: hyperthyroidism is more common than hypothyroidism
false
what are the primary defects that cause hyperthyroidism?
1) thyroid tumor
2) Graves disease (autoimmune)
3) thyroiditis (inflammation of Thyroid)
4) thyrotoxicosis factitia (too much TH is EATEN)
symptoms/concsequences of hyperthyroidism
A) abnrmal concentrations of circulating hormones- high TH, low TSH
B) goiter (only in graves disease)
C) up-regulation of metabolic and nervous systems
D) ocular symptoms
how is hyperthyroidism treated?
1) surgery, radioactive iodine
2) remove entire gland
3) treat with drugs
how do the drugs that treat hyperthyroidism work?
they block activity of enzyme in the TH production sequence
why is hyperthyroidism of special concerns to dental care
- you must avoid catecholaminergic drugs (their receptors are overly expressed in the body)
- thyroid storm
- salivary glands can be damaged after radiation therapy
