EX 2; Thyroid Gland Flashcards
What is the gross anatomy of the thyroid
2 lobes located inferior to the larynx one of the largest endocrine glands 4 cm long/wide 20 grams
What is the vascularization of the thyroid gland
more capillaries per gram than the kidney
The internal structure of the thyroid consists of what
hollow follicles formed by spheres of epithelial cells; follicles are filled with colloid, lots of protein
The follicular cells of the thyroid regulate production of what
two iodine-containing hormones
What is thyroid hormone synthesis stimulated by
TSH, which comes from the pituitary
Iodide is transported into follicular cells and then does what
diffuses into the colloid
Follicular cells also synthesize this, which is exocytosed into colloid
thyroglobulin; lots of tyrosine
Iodidie oxidized by this and is linked to thryoglobulin; attaching iodide to tyrosine creating MITs and DITs
thyroid peroxidase
The mono-iodo-tyrosine and di-iodo-tyrosie combine to form what
MIT + DIT = T3
DIT + DIT = T4
The thyroid hormone stored in colloid is attached to thyroglobulin, why is this necessary
the protein backbone is not lipid soluble, so it traps the hormone
What three additional actions does TSH stimulate
stimulates iodide uptake
protein synthesis
mitosis in follicular cells; hypertrophy and hyperplasia
Thyroglobulin droplets are pinocyotsed into follicle cells and the droplets fuse with what and what occurs
lyosomes and T3 and T4 are released by lysosomal hydrolysis and diffuses into capillaries
10% of secreted thyroid hormone is what variety
T3
80% of T4 is converted to T3 in which organs
liver and kidney (and certain target cells)
Where are the receptors for thyroid hormone located and what are the different forms
they are in most cells of the body
α and β forms
Expression of receptor isoforms differs in respect to what two things
stage of development (α first) target tissue (regulate and stimulate cell metabolism)
These two things combined regulate gene transcription
dimerized receptors + TH
Thyroid hormone is used to stimulate what
metabolism
thyroid hormone stimulates cellular metabolism by increasing the activity of what three things
Na/K-ATPase activity
increases substrate availability
produces heat
What does thyroid hormone do to the mitochondria
increases size and number
Insufficient TH during fetal development causes what condition
cretinism
True or False
diseases of the thyroid gland are the most common of endocrine diseases
True
How common is thyroid disease in women and in men
2-5% in women (childbearing years most common)
0.5% of men
twice as many people have thyroid disease than the number of people diagnosed
What is the primary cause of hypothyroidism
a primary defect in the thyroid gland
95% due to iodine deficiency
What are three consequences of an iodine deficiency
insufficient production of TH
lack of negative feedback
growth of goiter because hypertrophy or hyperplasia of follicular cells
Hypothyroid due to an iodine deficiency was primarily reversed due to what for additive
iodized salt
This is also known as Hashimoto’s, which affects the enzymes synthesizing thyroid hormone
autoimmune thyroiditis
What two additional primary defects can lead to hypothyroidism
damage or destruction due to surgery/radiation, etc.
dysfunction associated with other illness
What is a second defect that can result in hypothyroid
problem in the pituitary; release or receptor issue
What are some mild symptoms of hypothyroid
cold sensitivity
low metabolism
weight gain
What are some moderate symptoms of hypothyroid
fatigue
poor circulation
GI/mental function is sluggish
What are some severs symptoms of hypothyroid
myxedema due to accumulation of glycosaminoglycans in the ECF
What are four primary defects that can cause hyperthyroid or thyrotoxicosis
thyroid tumor
Graves disease
thyroiditis
thyrotoxicosis facitia
This is when antibodies to TSH receptor stimulate the gland, the feedback mechanism is disrupted, and is more common in women
Grave’s disease
This is when too much thyroid hormone due to ingesting of endogenous thyroid hormone
thyrotoxicosis factitia
What are four symptoms of hyperthroid
abnormal levels of circulating hormone
goiter
metabolic and nervous system symptoms; upregulation
ocular symptoms; fat pad behind eye is bulging
What are some options for treatment of hyperthyroid
surgically/radioactivity destroy the gland
anti-thyroid drugs
What are some dental problems associated with hypothyroid
abnormal response to drugs; increased sensitivity
myxedema; extra CSF
diminished cardiac and respiratory functions
What are some dental problems associated with hyperthyroid
early eruption of teeth
must avoid catecholaminergic drugs; sensitive to epinephrine, sympathetic already on “high alert”
thyroid storm
salivary gland damage due to radiation treatments
Thyroid hormone up regulates these receptors
beta adrenergic
Upregulation of beta adrenergic receptors by thyroid hormone increases sensitivity to what
catecholamines
When the thyroid hormone up regulates beta adrenergic receptors, what does this due to the sympathetic system
involved with the sympathetic system; NE and E
increasing HR and dilating respiration
The thyroid hormones also regulate production of this
GH
Thyroid hormone is important for this development
CNS development and function
Thyroid hormone regulates what in adults
normal neural responses in adults; hence why if you have limited TH in fetal development = cretinism
