1. By Katie Hall and Grace Ellis
THYROID GLAND
By Katie Hall and Grace Ellis
A.P. Biology

2. Location in the Body

4. Hormones Released
The thyroid converts iodine into two thyroid hormones:
Thyroxine(T4)
6 times more than T3
minority of cell response
amine (peptide) hormone
Triiodothyronine (T3)
Majority of cellular response
converted from T4 in the cell by taking one iodine
Calcitonin
peptide hormone

5. Functions of the Hormones
Calcitonin- lowers blood calcium level
Thyroid hormone - acts on target cells throughout the body to control bioenergetics; help maintain normal blood pressure, heart rate, and muscle tone; and regulate digestive and reproductive functions
Evolution
During evolution hormones begin to take on different functions between species. Such as thyroxine which usually regulates metabolism, stimulates the reabsorption of a tadpole’s tail.

6. Functions of the Hormones
Peptide Hormones create a rapid, short lived response.
Peptide hormones are made of amino acids.
Steroid Hormones create a slow, long lived response. Steroid hormones are made of lipids.

7. Thyroid Hormones are Regulated by...
Hormone Cascade Pathways
Sets of hormones target the thyroid gland
Signals go through pathway to be redirected to affect thyroid
Hormones that cause release of hormones from thyroid come from...
1) Hypothalamus
2) Anterior pituitary
Hormone cascade pathways related to the thyroid gland often involve…
Negative Feedback
Accumulation of end product of a process slows the beginning
Counteract the initial change

8. Feedback Loops 1 Thyroid hormone levels drop below the normal range.
Hypothalamus secretes thyrotropin releasing hormone (TRH) into the blood. Portal vessels carry TRH to the anterior pituitary.
TSH stimulates thyroid gland to secrete thyroid hormone (T3 and T4) into the circulatory system. 4
Thyroid hormone blocks TRH release. 5 2
TRH causes the anterior pituitary to secrete TSH (thyrotropin; thyroid-stimulating hormone) into the circulatory system. 3
Thyroid hormone levels increase in blood & body tissues (back to normal range). 5

9. Negative-feedback loop prevents overproduction of thyroid hormone
Feedback Loops: Negative Feedback
Negative-feedback loop prevents overproduction of thyroid hormone
Normal range
TRH release is blocked
T3 & T4 ↑
TSH
TRH
Hormone cascade pathway:
T3 & T4 levels too low
TRH released ∞

10. Thyroid Disease Thyroid disease: any dysfunction of the thyroid gland
Thyroid disease: any dysfunction of the thyroid gland
Hyperthyroidism: occurs when thyroid gland makes more thyroid hormones than the body needs
Hypothyroidism: occurs when thyroid gland does not make enough thyroid hormones
Thyroid cancer: uncontrolled cell division on thyroid
Goiter: enlargement of the thyroid gland due to iodine deficiency
Thyroid nodules: lumps in the thyroid gland
Thyroiditis: swelling of the thyroid
goiter
Thyroid hormone contains iodine; iodine allows more thyroid hormone to be made.
Physicians use a radioactive isotope of iodine to detect abnormal iodine uptake.
This thyroid scan indicates thyroid disease.

11. Thyroid Disease Hyperthyroidism Hypothyroidism Causes
Excess of thyroid hormones
Graves’ disease (autoimmune disorder)
Excess of iodine
Taking excess of synthetic thyroid hormone
Thyroid hormone deficiency
Hashimoto's disease (autoimmune disorder)
Most Commonly Affects…
Women & people over 60
Symptoms
*Metabolic dysfunction!
Weight loss
Fatigue or muscle weakness
Heat intolerance
Rapid heartbeat
Weight gain
Muscle pain
Cold intolerance
Slowed heartbeat
Treatment
Medicines, radioiodine therapy (used to destroy thyroid tissue not removed by surgery), or thyroid surgery
Medicines, surgical removal of part or all of the thyroid, radiation treatment of the thyroid

12. Citations
“Thyroid Diseases.” MedlinePlus, National Institutes of Health, 31 Jan. 18AD,
medlineplus.gov/thyroidcancer.html.
The American Cancer Society medical and editorial content team. “Radioactive
Iodine (Radioiodine) Therapy for Thyroid Cancer.” American Cancer Society, American Cancer Society, 15 Apr. 16AD,