Thyroid Flashcards
What does the hypothalamus secrete on the thyroid?
Thyrotropin releasing hormone
How does TRH reach the pituitary gland?
Via portal circulation
What does the pituitary gland produce when it is stimulated by TRH?
The pituitary gland produces and secretes thyroid stimulating hormone (TSH)
What is the mediate stimulus to the thyroid cells?
TSH
What do the thyroid cells secrete when they are stimulated by TSH?
T3 and T4
What does T3 stand for?
triiodothyronine
What does T4 stand for?
thyroxine
What makes T3 and T4 unique compared to the rest of the body?
They contain iodine
What absorbs iodine? How does this effect the thyroid?
- Iodine is absorbed in the intestine
- Iodine is taken in by the thyroids follicle cells
Describe the iodine concentration of the thyroid gland compared to the plasma
The thyroid gland typically achieves iodine concentrations 50 times greater than that of the plasma.
How does iron form T4 and T3
Iodine is then used in combination with other amino acids to form T4 and T3.
How is T3 and T4 transported in the blood?
In the blood, most T3 and T4 are transported bound to alpha globulins and albumin.
What is the principle protein involvedin transporting T3 and T4?
The principle protein involved is known as thyroxine-binding globulin (TBG).
Do bound T3 and T4 stimulate target tissues?
NO! only unbound ones stimulate target tissues
Are quantities on unbound T3 and T4 large or small?
Small
What are examples of thyroid target tissues in the body?
Virtually all cells
What is the effect of thyroid hormone?
- Metabolic
- Promotes utilization of carbohydrates, proteins, and lipids
What are the primary effects of thyroid hormones?
- Aerobic energy metabolism
- Glucose metabolism
- Protein metabolism
- Lipid metabolism
- Ion transport
What are examples of secondary effects of thyroid hormones?
- Growth/development
- Cardiac output
- Ventilation
- CNS activity
- Thermoregulation
- Muscle function
- GI activity
- Reproductive functions
What are examples of basic problems that you can have with your thyroid?
- Excessive T3 and T4
- Deficient T3 and T4
- Malfunction of the gland itself
- Defect in the anterior pituitary/hypothalamus control system
Describe thyroid hormone hypofunction
Thyroid hormone secretion is inadequate to maintain normal levels of target tissue stimulation
What causes most adult hyposecretion of thyroid?
-Surgical resection or radiation therapy after a hyperactive state
What is disorder seen in newborns where normal growth and tissue differentiation are impaired.
Cretinism
Other thyroid hypoperfusion causes
- Penetrating wounds to the neck that produce inflammation.
- Bacterial or viral infections especially to the mouth or throat region
- Iodine deficiency
- Insufficient stimulus by hypothalamus/pituitary
- Therapeutic drugs that have thyroid blocking side effects
- Pregnancy and puberty
