1.  Superior thyroid artery

-From the external carotid

2.  Inferior thyroid

-from the subclavian

Bruit

(The unusual sound blood makes as it rushes past a obstruction)

Where does the thyroid receive its innervation from?

adrenergic and colonergic?

External Laryngeal and recurrent larengeal 

Adrenergic:  cervicle ganglia

Colonergic:  vagus nerve

A center is called the lumen and is composed of colloid.

The single layer of epithelial cells surrounding the lumen are called follicular cells.

There is also C-cells sandwiched in between follicles.

1.  Hypothalamus secrets thyroid releasing hormone

2.  Enters the blood stream at median eminence

3.  Travels down through the long portal veins

4.  Enters the capillary beds of the ant. Pit.

- aka the adenohypophysis

-aka pars distalis

5.  Ant. Pit. releases TSH which leaves in the venous blood

6.  Thyroid releases T3 and T4

TSH

Excess leads to a goiter!

1.  TSH (catecholamine) binds to and activates the TSH receptor.

2.  The TSH receptor then activates the cAMP cycle.

3.  GDP is replaced by GTP

4.  alpha subunit releases from beta and gamma subunits

5.  protein kinase A  is activated

6. Number of phosphorylation RXNs result in synthesis and release of hormones

Thought of as the second pathway for thyroid hormone release (When TSH is REALLY HIGH) 

1.  Phospholipase C catalyzes the formation of second messengers IP-3 and DAG.

2.  IP-3 activates Protein Kinase C

3.  Thyroid hormone is synthesized and released.

T4 (thryoxine) is converted to T3 (Triiodothyronine)

1.  CNS development (esp. early in life)

2.  Body growth and development

3.  Basal energy regulation

4.  Metabolism

5.  Regulates its own secretion

amino acid (Tyrosine)

TBG-Thyroxine binding globulin

-A Carrier Protein

1.  Iodide is trapped in the folicular cell by the Sodium/iodide symporter.

2.  Pendrin transports iodide ion into lumen (colloid space)

3.  Iodide ion is oxidized into iodine

4.  Enzymes (esp. thyroid peroidase) allow the addition of one or two iodine to the tyrosine residue of thyroglobulin.

5.  two DITs form T4 while one MIT and one DIT form T3.

6.  Colloid is pinocytosed, combines with lysosome, and the resulting T3 and T4 are excreted into blood.

1.  Ionization of tyrosines on thyroglobulin

-aka Organification

2.  Synthesis of T3 or T4 from 2 iodotyrosines

-The actually combining of MITs and DITs

These amino acid hormones use an intracellular receptor system similar to steroids.

Thyroid hormones also need a Thyroxin binding globulin as a carrier protein while in the blood.

FALSE!

Graves disease is more common in women!

Bulging of the eyes as a result of Grave's Disease is known as ______?

INCREASE in T4 and T3

Decrease in TSH

Radioactive iodine isotopes (RAI-131)

Only the thryoid is affected by these isotopes

They're hyperthyroidism was likely treated by having their thyroid removed either surgically or by use of radioactive iodine (RAI-131).

Thus they need synthetic thyroid supplements.

Cases in which people ate burgers that had thyroid hormone in them and had a temporary case of thyrotoxicoses. 

ANY MORE OF THOSE HAMBURGERS LEFT?

1.  Subacute painful

2.  Subacute painless

-autoimmune, more women than men

3.  Acute suppurative

-infection

4.  Reidel's thyroiditis

-fibrous infiltration, normal or hypofunction

HASHIMOTO'S THYROIDITIS!

Autoimmune function

Diffuse goiter and increase thyroid hormone

What's another name for hypothyroidism?

What is a condition related this?

Myxedema

Results in cretinism

DECREASED T3 and T4

Increased TSH

Primary hypothyroidism results from atrophy or loss of thyroid tissue

Secondary hypothyroidism is from a pituitary diffeciency

Tertiary hypothyroidism is from a problem in the hypothalamus

It is a skin condition on the shin area that has swollen, itchy patches of skin.

Associated with HYPERthyroidism (not hypo!)

Cretinism

-Growth and mental retardation

-Dwarfism, overweight, malocclusion, wide set eyes, poor muscle tone.

Papillary/ mixed papillary(look like fronds)/ follicular

Person has enlarged, hard nodes and cough and horseness of breath. 

Has presence of psomma bodies

Multiple Endocrine Neoplasms

MEN-1 

The three P's

1.  Pituitary (65%)

2.  Parathyroid (88%)

3.  Pancreas (81%)

MEN-2A

Thyroid Medullary, parathyroid, and adrenal

 Pheochromocytoma

Men-2B

Mucousal Neuromas!

MEN-1 (Multiple Endocrine Neoplasms)

Affects the Pituitary, Parathyroid, and Pancreas

MEN-2A

Thyroid medullary carcinoma is a very aggressive condition, may require preventative thyroidectomy.

Describe the process of iodide trapping.

1.  Iodide circulating in the blood stream is cotransported with sodium ions across the follicular cell plasma membrane.

2.  Once inside the follicular cell, the bulky iodide ion can't diffuse back into the interstitual fluid...IT'S TRAPPED!

3.  Sodium is eventually pumped back out of the cell by the sodium/potassium -ATPase

It is a protein present in the colloid that contains rings of tyrosines.  When combined with iodide, it can become monoiodotyrosine (MIT) or diiodotyrosine (DIT).

The DIT either combines with another DIT or a MIT to make T4 or T3 respectively.