Hormones that Affect Metabolism

Two Major Glands

• Thyroid Gland• Parathyroid Gland

Thyroid Gland• Thyroxine (T4)• Triiodothyronine (T3)

– Both need iodine to be made.– Used to oxidize sugar and other nutrients.– More T4 in the blood will “boost metabolism”

Hypothyroid or HyperthyroidIf the thyroid gland produces T4 and T3,

hormones that regulate metabolism, what would happen if:

a)The thyroid stopped producing T4 and T3? (hypothyroidism)b)The thyroid could not stop producing T4 and T3? (hyperthyroidism)

CalcitoninCalcitonin is also released by the thyroid, and it counter-acts parathyroid hormone (PTH) by:

•Inhibiting Ca2+ absorption by the intestines•Inhibits Ca2+ reabsorption in the nephrons of the kidney

Thyroid Negative Feedback Loop

Acronyms:• TRH – Thyroid Releasing Hormone• TSH – Thyroid Stimulating Hormone

What happens if the body lacks iodine?

Goiter

Parathyroid Glands• Four groups of cells on the thyroid gland.• Release a hormone called parathyroid

hormone, or “PTH”.– PTH raises the calcium levels in the blood.

Negative Feedback

Human Growth Hormone (HGH)

• Too much? - Giantism• Too little? - Dwarfism• Produced in and released from the anterior pituitary gland.

Human Growth Hormone• Cause cells to grow in size and in number.• Promotes protein synthesis.• Promotes the breakdown of fats.

– ↑ GH, muscles use fatty acids as energy– Loss of fat during growth spurts

Growth Hormone Doping?• Some athletes believe that taking human

growth hormone supplements will increase their athletic performance.