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

89534

Card Set

Thyroid Hormones S2M1

Description

Biochem

Updated

2011-08-12T23:15:06Z

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