Section 8.3: Hormones that affect MetabolismPages 384-387

Recap•Hormones that affect blood sugar

▫Insulin, glucagon, epinephrine, norepinephrine and cortisol

•Adrenal Glands•Glucocorticoids and Mineralocorticoids •Diabetes

▫Type I, II and III

3 Glands that affect Metabolism

1. Thyroid Gland

2. Parathyroid Glands

3. Anterior Pituitary Glands

Thyroid Glands

1. Thyroid Glands•Located at the base of the neck, in front

of the trachea•There are two important thyroid

hormones▫1. Thyroxine (T4)▫2. Triiodothyronine (T3)

•Regulate body metabolism and the growth and differentiation of tissues.

Thyroxine (T4)Individuals who secrete high levels of T4

oxidize sugars and nutrients at a faster rate

•60% of oxidized glucose is released as heat•40% transferred to ATP•This added energy reserve is usually

consumed during activityResult?•Lack of weight gain

Thyroxine (T4)Individuals who secrete low levels of T4

cannot break down sugars and nutrients as easily

•Excess blood sugar converted into liver and muscle glycogen

•Once the glycogen stores are filled converted to fat

•Low levels of T4 leads to muscle weakness, cold intolerance and dry skin

The Feedback System•If the metabolic rate decreases receptors

in the hypothalamus are activated•Nerves secrete TRH (thyroid-releasing

hormone)•The release of TRH signals pituitary to

release TSH (thyroid-stimulating hormone) •TSH is carried by blood to thyroid gland

which releases T4•T4 increases metabolism or increased sugar

utilization

The Feedback System

Figure 3. page 385

nerves

blood

Decrease in metabolic rate TRH TSH Thyroxine (T4)

Increased utilization of sugar

Thyroid Disorders• Iodine is an important

component of both thyroid hormones (T3 and T4)

• When iodine levels begin to decline, the production and secretion of T4 drops

• The level of TSH increases and cells of the thyroid continue to develop

• The thyroid enlarges goiter or the swelling of the neck area

Figure 4. page 385

2. Parathyroid Glands• 4 small parathyroid

glands exist in the thyroid gland

• Usually hormones or nerves regulate endocrine glands parathyroid is the exception

• Respond to chemical changes in surrounding environment

Parathyroid Gland and Calcium•Low calcium levels release parathyroid

hormone (PTH)

•PTH causes calcium levels to increase and phosphate levels to decrease

•PTH acts on 3 different organs: the kidneys, the intestines and the bones

Parathyroid Gland and Calcium•PTH causes:1.The kidneys and gut to retain calcium2.Calcium release from the bones

•Bone cells break down calcium is separated from phosphate ions

•Calcium is reabsorbed, phosphate is excreted in the urine.

Parathyroid Gland and Calcium•After calcium levels increase, the release

of PTH is inhibited to ensure calcium levels are not too high.

•If calcium levels increase beyond demand:1.The prolonged break down of bone2.High levels of calcium could collect in

blood vessels and form stone-like structures

PTH Illustration

Figure 5. page 386

Low Levels of Vitamin D

Growth Hormone (GH)•Also known as somatotropin•Created by the anterior pituitary •Low levels of GH dwarfism•High levels of GH gigantism •Affects most cells in the body, especially

cartilage and bone cells•Increases # of cells (hyperplasia)•Increases size of cells (hypertrophy)

Growth Hormone (GH)•Promotes protein synthesis while

inhibiting protein degradation•Stimulates ribosomes to follow the

genetic instructions for protein synthesis•Promotes the elongation of long bones•Causes a switch in cellular fuels from

glucose to fatty acids•As you get older, GH decreases

Summary of Hormones

Table 1. page 387

8.5 Anabolic SteroidsPage 388-391

Anabolic steroids:•Designed to build excessive muscle and mimics the traits of the sex hormone testosterone

•Can provide greater lean muscle development and increased strength

•Prematurely fuse growth plates in the long bones

•Can cause mood swings and feelings of rage

Anabolic steroids don’t:

•Provide increased agility or skill level

•Enhance the ability of cardiovascular system to deliver oxygen

What are the side effects of prolonged

use of anabolic steroids?