1. Hormones that affect metabolism: Thyroid Gland
located at base of neck
two important thyroid hormones (which regulate body metabolism, growth, and differentiation of tissues)
thyroxine (T4)
triiodothyronine (T3)

2. Hormones that affect metabolism
Three different glands affect metabolism
thyroid gland
helps regulate body metabolism (glucose oxidation rate)
produces three hormones
triiodothyronine, thyroxine, calcitonin
parathyroid gland
produces parathyroid hormone
helps regulate calcium levels in blood and lower phosphate levels
anterior pituitary gland
produces growth hormones and regulatory hormones

3. Hormones That Affect Metabolism
Gland
Hormone
Action
Thyroid
Thyroxine
metabolism
Calcitonin
↓’s calcium levels in blood
Parathyroid
PTH
↑’s calcium levels and ↓’s phosphate levels
Anterior Pituitary Gland GH
Growth of bones and protein synthesis

4. Thyroid Gland
individuals who secrete higher levels of thyroxine oxidize sugars and other nutrients at a faster rate
When glycogen stores are filled, excess sugar is converted to fat
control of thyroid hormones is accomplished by negative feedback

5. Feedback Control Loops for Thyroid Hormones

6. Feedback loop...
receptors in hypothalamus are activated if the metabolic rate decreases
nerve cells secrete TRH (thyroid releasing hormone)
this stimulates pituitary to release TSH (thyroid stimulating hormone)
carried by blood to thyroid gland which then releases thyroxine which raises metabolism by stimulating sugar utilization by cells
high levels of thyroxine cause pathway to be turned off, inhibiting release of TRH
VIDEO of thyroxine
Thyroid gland also contains calcitonin
hormone acting on bone cells to lower level of calcium found in blood

7. Oh no!
when inadequate amounts of iodine are obtained from the diet, thyroid enlarges, producing a goiter.
If thyroxine levels ↓’s, TSH ↑’s, and thyroid is stimulated more and more
Thyroid cells continue to develop and thyroid enlarges

9. Parathyroid Glands
Four parathyroid glands hidden within larger thyroid gland
Usually nerves or other hormones regulate the endocrine glands with the parathyroid glands being the exception
These maintain homeostasis by responding directly to chemical changes in their immediate surroundings (low calcium levels)
PTH raises calcium levels in the blood
 PTH (parathyroid hormone) also help activate vitamin D. (Low levels of vit D cause rickets!)

10. Rickets and Goiters...

11. Regulation of Blood Calcium
Endocrine System Control
Regulation of Blood Calcium
Feedback
calcitonin
 kidney reabsorption of Ca++
thyroid
Ca++ deposited in bones
high
 Ca++ uptake in intestines
blood calcium level (10 mg/100mL)
low
activated Vitamin D
 kidney reabsorption of Ca++
parathyroid
bones release Ca++
parathyroid hormone (PTH)

12. Dangers of high calcium levels VIDEO- “the Doctors”

13. Human Growth Hormone (aka Somatotropin)
Too little = dwarfism
Too much = gigantism
Released by Ant. Pit.
GH increases cell size in muscle cell and connective tissue by promoting Protein Synthesis (increasing Amino Acid uptake)
Promotes fat burning
Dec. Levels of GH with age

14. HGH and Controversy...
Should you take it?

15. GH affects all body cells BUT mainly bone cells
Acromegaly- bones of jaw, forehead, fingers and toes increase in width, once other bones can no longer increase in length (growth plates fused)