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)

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

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

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

Feedback Control Loops for Thyroid Hormones

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

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

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!)

Rickets and Goiters...

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)

Dangers of high calcium levels VIDEO- “the Doctors”

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

HGH and Controversy... Should you take it?

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)