Term
| T/F: The thyroid gland is follicular, bilobular (butterfly shaped) and sits a top of the larynx. |
|
Definition
| False; it sits a top of the trachea which is just below the larynx |
|
|
Term
| The follicles in the thyroid gland consist of a single layer of epithelial cells called ____________ that enclose a ___________center. |
|
Definition
Follicular or Thyroid cells
Colloid |
|
|
Term
| The colloid center is a medium of ____________ that is distributed evenly. |
|
Definition
| very high concentrated protein |
|
|
Term
| The follicular or Thyroid cells are said to not only line the follicles but also _______. |
|
Definition
Secrete thyroid hormones
T4 and T3 |
|
|
Term
|
Definition
Thyroxine
Triiodothyronine |
|
|
Term
| Where are thryoid hormones dervied from? |
|
Definition
|
|
Term
| What is unique of the synthesif of thyroid hormones? |
|
Definition
| That is starts within the Thyroid cell but then is completed outside the cell in the colloid. |
|
|
Term
| What element is needed for Thyroid hormone synthesis? |
|
Definition
|
|
Term
| Where and how does Iodine get to the inner membrane? |
|
Definition
| Since I2 in the plasma is low, an active transport mechanism traps and removes an excess 3-40x [blood I2] I2 from within the thyroid cell. |
|
|
Term
| Where is the I2 trap located? |
|
Definition
| On the basal membrane (basement) |
|
|
Term
| Where does synthesis of Thyroglobulin take place? |
|
Definition
|
|
Term
| Thyroglobulin is a large glycoprotein with 4 subunits and contains how many tyrosine residues per molecule? |
|
Definition
|
|
Term
| In the apical membrane what happens to the I2 and what enzyme is responsible for this? |
|
Definition
Gets oxidated from I- to I+
Enzyme = Thyroid peroxidase (TPO) |
|
|
Term
| What is the rate limiting step of thyroid hormone synthesis? |
|
Definition
|
|
Term
| Where does the I+ get incorporated into? |
|
Definition
| Into the tyrosine residues of the Thyroglobulin molecules to make either MIT or DIT |
|
|
Term
| The iodination of TG is initiated in the _______________ but is completed within the ____________. |
|
Definition
|
|
Term
| What 2 molecules combine to form T4? |
|
Definition
|
|
Term
| What 2 molecules combine to form T3? |
|
Definition
|
|
Term
| T/F: The TG that has MIT, DIT, T3 and T4 is stored in the colloid and is released when the body needs it. |
|
Definition
|
|
Term
| When the body needs it TG is engulfed by the apical membrance to form ____________. |
|
Definition
|
|
Term
| What happens to the colloid droplets as they transverse the follicular cell? |
|
Definition
| They form a phagosome after encountering a lysosome. Within the phagosome the lysosome releases enzymes that digest the TG molecules thus releasing the individual T4 and T3. |
|
|
Term
| What happens to the unused MIT and DIT residues? |
|
Definition
They de-iodinate inside the thyroid cell via deiodinase.
(Recycling of tyrosine for future use) |
|
|
Term
| T/F: T3 and T4 are released into the blood where they are bound to proteins that are made in the liver. |
|
Definition
|
|
Term
| Which binding protein binds both T3 and T4? |
|
Definition
| Thyroxine binding globulin (TBG) |
|
|
Term
| TBG is responsible for __________ % of bound T4. |
|
Definition
|
|
Term
| Transthyretin aka thyroxine prealbumin only binds _______. |
|
Definition
|
|
Term
| T/F: Albumin bind both T3 and T4 just on a smaller extent. |
|
Definition
|
|
Term
| Does TBG preferentially bind T3 or T4. |
|
Definition
|
|
Term
| Whats the total # of T4 in plasma? |
|
Definition
|
|
Term
| How much T4 is free in the plasma? |
|
Definition
|
|
Term
| How much total T3 is there in the plasma? |
|
Definition
|
|
Term
| How much T3 in the plasma is free? |
|
Definition
|
|
Term
| Which form (bound or free) is responsbile for the biological activity of the hormone? |
|
Definition
|
|
Term
| How does metabolism of thyroid hormone occur? |
|
Definition
| sequential deiodination to thyronine in the urine |
|
|
Term
| What % of T4 is metabolized to T3 via Deiodinase 1 and 2? |
|
Definition
|
|
Term
| Where is Deiodinase 1 located? |
|
Definition
| Thyroid, liver, and kidney |
|
|
Term
| 35% of T4 is metabolized to ____________ |
|
Definition
| reverse T3 via Deiodinase 3 |
|
|
Term
| Where is Deiodinase 3 found? |
|
Definition
Brain, placenta, fetal tissues
(needed for CNS development) |
|
|
Term
| What happens to the unused T3/T4? |
|
Definition
~ 25%
it gets removed and excreted in feces |
|
|
Term
| What regulates the thyroid gland? |
|
Definition
TSH
Thyroid Stimulating Hormone released from the A.P |
|
|
Term
| Which chain (alpha or beta) is unique to each hormone and confers specificity of action for TSH? |
|
Definition
|
|
Term
| T/F: TSH is released from thyrotropes and thyrotropes make up 5-15% of cells. |
|
Definition
|
|
Term
| Is TSH released into the blood with proteins or without carrier proteins? |
|
Definition
without
So half life ~ 60 mins |
|
|
Term
| TSH has what types of effects and actions? |
|
Definition
1. Increases I2 pump activity to increase thyroid hormone synthesis and release
2. Increases TG synthesis
3. Increases Thyroid peroxidase activity
4. Increases endocytosis of colloid droplets
5. Increases lysosomal activity and TG proteolysis
|
|
|
Term
| What is the net effect of TSH in the thyroid? |
|
Definition
| Increase in thyroid hormone release and a concomitatnt decrease in colloid volume within the thyroid |
|
|
Term
| T/F: TSH secretion is increased when exposed to heat. |
|
Definition
| False; when exposed to cold |
|
|
Term
| What 2 things are associated with a rise in TSH release? |
|
Definition
|
|
Term
| What 2 things regulate the TSH secretion? |
|
Definition
Under hypothalamic regulation
TRH = Stimulates
SS = Somatostatin = Inhibits |
|
|
Term
| How do opiates decrease TSH? |
|
Definition
|
|
Term
| Which nuerotransmitters increases TSH levels by increasing TRH? |
|
Definition
|
|
Term
| T/F: Thyroid hormones increase TSH release. |
|
Definition
False; it is under negative feedback.
They act directly at the pituitary to decrease TSH release or they can act on the hypothalamus to decrease TRH release/ increase SS release. |
|
|
Term
| How do Thyroid hormone receptors function as hormone activated transcription factors? |
|
Definition
If hormone is bound = change shape in receptor that causes it to function as transcriptional activator
If no hormone bound = receptors bind DNA which leads to transcriptional repression |
|
|
Term
| Which form (T4 or T3) carry out all the actions of the thyroid hormones? |
|
Definition
|
|
Term
| T4/T3 induces calorigensis. What occurs? |
|
Definition
Increased O2 consumption in nucleus and mitochondria
Increases cellular respiration
Produces heat
Increases BMR |
|
|
Term
| T4/T3 have a biphasic effect on protein synthesis. What does this mean? |
|
Definition
If low to normal levels of T3 = increase protein synthesis via GH and Na+and K+ATPase
If high levels = Protein catabolism via increase in lysosomal enzymes |
|
|
Term
| How does T3/T4 levels affect carbohydrate metabolism? |
|
Definition
If low to normal T3 = decrease blood glucose
If high = induce glycogenolysis thus increasing blood glucose levels
|
|
|
Term
| How does T3/T4 affect lipid metabolism? |
|
Definition
1. It induces lipid breakdown in fat tissue via an hormone sensitive lipase
2. Sensitizes fat tissues to lipolytic effects of other hormones (GH, Epi, Cortisol)
3. Decreases cholesterol by increasing both its excretion and degradation |
|
|
Term
| Why is T3/T4 needed for CNS development? |
|
Definition
| Essential in neural development, myelination, differentiation and migration of cells. |
|
|
Term
| T3/T4 net effect on the cardiac system is |
|
Definition
| increase in cardiac function by increasing the B-receptors in the cardiac muscles |
|
|
Term
| T/F: Only hyperthyroidism is associated with having groiters? |
|
Definition
|
|
Term
| What type of goiter develops in hyperthyroidism? In hypothyroidism? |
|
Definition
Hyper = Toxic groiter - hard and follicle cell hypertrophy
Hypo = Nontoxic groiter - Soft and diffuse |
|
|
Term
| What are 3 classes of Hyperthyroidism? |
|
Definition
1. Autoimmune
2. Thyroid Tumor
3. Pituitary tumor |
|
|
Term
| Both Autoimmune and thyroid tumor associated Hyperthyroidism have an increase in T4/T3 secretion and a ____________in TSH secretion. |
|
Definition
|
|
Term
| With a pituitary tumor there is a ___________ in TSH and T4/T3 secretion. |
|
Definition
|
|
Term
|
Definition
|
|
Term
| What are some clinical manifestations for Hyperthyroidism? |
|
Definition
1. Warm, rosy skin, fine hair, early gray, friable
2. Exophthalmos, infiltrative ophthalmopathy
3. Thyroid storm = lead to death
4. Increase in intestinal motility/emptying
5. Can sit still. ADD
6. kids = linear growth; adults = tremors
7. High BMR, heat intolerance, insuline resistance and lipolytic |
|
|
Term
| T/F: Graves disease is more prevalent in women but men can get more severe clinical manfestations. |
|
Definition
| True (5-10x greater in women) |
|
|
Term
| Graves disease is an autoimmune disoder that has a defective ____________ which results in ________ induction of B-lymphocytes. |
|
Definition
T suppressor lymphocytes
T-helper |
|
|
Term
| The B lymphocytes make stimulating antibodies called ______________ and _____________ |
|
Definition
Long acting Thyroid stimulator (LATS)
Thyroid stimulating Immunoglobulins (TSI) |
|
|
Term
| What are 3 ways to treat Graves disease? |
|
Definition
1. Anti-thyroid therapy
2. Thyroidectomy
3. Radioactive Iodine |
|
|
Term
| How do thioamides work in the anti-thyroid drug therapy? |
|
Definition
They inhibit the thyroid peroxidase enzyme.
This way it doesnt damage the gland but will need continuous treatment |
|
|
Term
| What are some other possible causes for hyperthyroidism? |
|
Definition
1. Toxic nodular goiter
2. Thyroid carcinoma
3. Hypersecretion of Tsh
4. Thyrotoxicosis Factitia |
|
|
Term
| What is Thyrotoxicosis Facitia? |
|
Definition
Thyrotoxicosis without hyperthyroidism (so no groiter)
Occurs due to ingestiong of thyroid hormones |
|
|
Term
| What are the 3 types of Hypothyroidism? |
|
Definition
1. Thyroprivic
2. Trophoprivic
3. Goitrous |
|
|
Term
| Thyroprivic Hypothyroidism is a loss in |
|
Definition
|
|
Term
| Trophoprivic Hypothyroidism is due to |
|
Definition
| Insufficient stimulation due to hypothalamic/pituitary disease |
|
|
Term
| Goitrous Hypothyroidism results due to |
|
Definition
| Defective biosynthesis of thyroid hormones |
|
|
Term
| 95% of Hypothyroid cases involve with 2 types? |
|
Definition
| Thyroprivic and Goitrous Hypothyroidism |
|
|
Term
| What are some clinical manifestations for Hypothyroidism? |
|
Definition
Exact opposite of Hyperthyroidism.
Cool skin, myxedema, lethargic, decreased intestinal motility, stiffness and slowness in mucle movements
Increased cold intolerance
decrease protein synthesis |
|
|
Term
| What are the 3 types of Thyroprivic Hypothyroidism? |
|
Definition
1. Primary Hypothyroidism
2. Congenital Hypothyroidism
3. Postablative Hypothyroidism |
|
|
Term
| In Primary Hypothyroidism the thyroid gland is destroyed because |
|
Definition
| There is TSH blocking antibodies that block the TG activity. |
|
|
Term
| Do you form a goiter in Primary Hypothyroidism? |
|
Definition
|
|
Term
| T/F: Congenital Hypothyroidism occurs in child born without a thyroid gland or when the thyroid fails to descend to the throat region. |
|
Definition
|
|
Term
| Trophoprivic Hypothyroidism or aka secondary hypothyroidism there is no loss of thyroid tissue but an interruption of its regulation. What are 2 causes for this interruption? |
|
Definition
1. Pituitary defect/injury
2. Tumor pressing on hypothalamus |
|
|
Term
| Whats an example of secondary hypothyroidism? |
|
Definition
|
|
Term
| T/F: Endemic groiter/cretinism (in kids) and Hashimoto's Disease are both a form of Goitrous Hypothyroidism and form a diffuse, nontoxic goiter. |
|
Definition
|
|
Term
| What substance found in cassava meal blocks I2 transport? |
|
Definition
|
|
Term
In Hashimoto's disease there is autoantibodies agaisnt ________ and __________.
(Humoral) |
|
Definition
|
|
Term
| In Hashimotos the T lymphocytes induce ___________________ |
|
Definition
| Cell mediated immunity (CMI) to inflitrate the thyroid tissue |
|
|
Term
| T/F: Hashimotos disease is due to the combo of both B and T cell immunity and leads to the loss of thyroid function. |
|
Definition
|
|
