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Thyroid Hormones S2M1
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What is the apical transport for Iodine
Pendrin
Pendrin syndrome
Absence of Pendrin used for transporting Iodine into the follicular cells for thyroid hormones
It causes hearing problems and hypothyroidism
What are the two essential ingredients to T3 and T4
Protein bound tyrosine and iodine
Iodine trap
Active transport on the basal side of the follicular cells that transports Iodine and Na into the cell
What are the ways that iodine can get into the follicular cells to make thyroid hormones
Pendrin transport
Iodine trap
Break down of MIT and DIT
What the 7 steps for making T3 and T4
1. ER in the Follicular cell makes Thyroglobulin then the Golgi glycosylates it
2. Thyroglobulin is exocytosed into the lumen colloid
3. Iodide is oxidized to Iodine by thyroperoxidase and binds to Thyroglobulin making MIT and DIT
4. Binding of DIT and MIT makes protein bound T3 and T4
5. Protein bound T3 and T4 are pinocytosed back into cell
6. Hormones and thyroglobulin are separated by lysosymes
7. MIT and DIT are recycled while T3 and T4 are released into blood stream
Iodide is oxidized to Iodine by
Thyroperoxidase
What lies between follicular cells
Tight junctions
Thyroglobulin in the thyroid gland contains a supply of
Hormone sufficient for three months
How do T3 and T4 compare
T3 is 3-4 times more potent then T4
Half life of T4 is 6 days
Half life of T3 is 1.5 days
95% of released hormone is T4
How much of T3 and T4 is bound to proteins in the blood
99%
In large target tissues, what happens to the T4
Some is activated to T3 and some to reverse T3 (rT3)
Most of the T3 in the system comes from
T4 broken down in tissues outside the thyroid gland
What are the proteins that T3 an T4 are bound to in the blood stream
Thyroxin binding protein (TBG) (80%)
Transthyretin (10%)
Albumin (10%)
What happens if a patient has a lack of Thyroxin binding globulin (TBG)
The patient is normal, T3 and T4 will simply float around freely till it arrives at a target organ
What benefit is the binding of the transport protein to T3 and T4
It has a longer half life
It can't be excreted while bound to a protein
Transcortin
Protein transport and binding agent for glucocorticoids
What is the binding protein for Estrogens and Androgens
Sex hormone binding globulin
The biological action of a given hormone is proportional to
The level of unbound hormone in the blood, not the total hormone
The pituitary gland in the negative feedback system only recognizes
Free Hormones
Myxedema
Hypothyroidism in adults
- reduced metabolic rate
- Subcutaneous edema (caused by excess hyaluronic acid)
What are the two most common endocrine issues
Diabetes and Thyroid deficiency
Hashimoto disease
Autoimmune disease in which the thyroid is gradually destroyed
In what geographical areas are people more prone to hypothyroidism and less prone, why
Prone in mountainous areas (lack of iodine)
Less prone near sea (its packed with iodine)
What are the signs of hyperthyroidism
Increased metabolic rate
Palpitations
Restlessness
What is it called when there is an enlargement of the thyroid gland
Goiter
What kinds of problems cause goiter
Iodine deficiency which causes a raise TSH levels
Antibody stimulating the thyroid (Graves disease)
Wolff-Chaikoff affect
High doses of iodine inhibit hormone release, used only for short term treatment
What are some inorganic anions that inhibit iodine uptake into the thyroid gland
Thiocyanate
Nitrate
Pertechnetate
Author
lancesadams
ID
89534
Card Set
Thyroid Hormones S2M1
Description
Biochem
Updated
8/12/2011, 11:15:06 PM
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