Hormones That Affect Hormones That Affect MetabolismMetabolism

Glands & MetabolismGlands & Metabolism

• Metabolism is the sum of the chemical reactions Metabolism is the sum of the chemical reactions required to live.required to live.

• Metabolism (metabolic rate) is affected by the Metabolism (metabolic rate) is affected by the thyroid, parathyroids and anterior pituitary gland.thyroid, parathyroids and anterior pituitary gland.

• The thyroid gland is situated just below the The thyroid gland is situated just below the larynx.larynx.

• The parathyroid glands sit on the thyroid.The parathyroid glands sit on the thyroid.• The pituitary gland is situated just below the The pituitary gland is situated just below the

hypothalamus.hypothalamus.

The Thyroid GlandThe Thyroid Gland

• The thyroid is located just below the larynx and it The thyroid is located just below the larynx and it secretes the hormone thyroxine.secretes the hormone thyroxine.

• ThyroxineThyroxine aids in the oxidation (breakdown) of aids in the oxidation (breakdown) of sugar and nutrients in the body.sugar and nutrients in the body.

• People that produce ample amounts of thyroxine People that produce ample amounts of thyroxine usually can eat a lot of food without gaining any usually can eat a lot of food without gaining any weight because it is broken down very quickly.weight because it is broken down very quickly.

• People that have People that have hypothyroidismhypothyroidism are the are the opposite…they have low levels of thyroxine and opposite…they have low levels of thyroxine and because of this they do not oxidize nutrients fast because of this they do not oxidize nutrients fast enough and they gain weight quickly.enough and they gain weight quickly.

Controlling the ThyroidControlling the Thyroid• The thyroid is brought into action by a negative feedback system The thyroid is brought into action by a negative feedback system

which involves the hypothalamus and pituitary gland.which involves the hypothalamus and pituitary gland.

• Low Metabolic Rate…Low Metabolic Rate…• Detected by the Detected by the hypothalamushypothalamus – it releases – it releases thyroid-thyroid-

releasing hormonereleasing hormone (TRH) which goes to the (TRH) which goes to the pituitary.pituitary.

• PituitaryPituitary receives TRH and produces receives TRH and produces thyroid-thyroid-stimulating hormonestimulating hormone (TSH) which goes into blood to (TSH) which goes into blood to get to thyroid gland.get to thyroid gland.

• Upon receiving TSH, the thyroid gland secretes Upon receiving TSH, the thyroid gland secretes thyroxinethyroxine which raises metabolic rate. which raises metabolic rate.

The Parathyroid GlandsThe Parathyroid Glands

• The parathyroids are four smaller glands found The parathyroids are four smaller glands found within the thyroid gland.within the thyroid gland.

• Their control/action is not under the influence of Their control/action is not under the influence of the nervous or endocrine systems – the the nervous or endocrine systems – the parathyroids respond directly to changes in their parathyroids respond directly to changes in their immediate surroundings.immediate surroundings.

• The parathyroids produce The parathyroids produce parathyroid parathyroid hormonehormone (PTH) which raises the levels of (PTH) which raises the levels of calcium in the blood.calcium in the blood.

Growth HormoneGrowth Hormone

• Growth hormone (Growth hormone (somatotropinsomatotropin) is made and released ) is made and released by the anterior pituitary.by the anterior pituitary.

• Growth hormone…Growth hormone…– Growth hormone causes tissues to increase in number and/or Growth hormone causes tissues to increase in number and/or

size. In muscles, the cells increase in size by promoting protein size. In muscles, the cells increase in size by promoting protein synthesis and inhibiting protein breakdown. In bones, the cells synthesis and inhibiting protein breakdown. In bones, the cells elongate and the skeleton lengthens.elongate and the skeleton lengthens.

– The growth hormone also promotes the breakdown of fats into The growth hormone also promotes the breakdown of fats into fatty acids which can actually replace glucose as the primary fatty acids which can actually replace glucose as the primary fuel. Glucose builds up in the blood – good for the brain – while fuel. Glucose builds up in the blood – good for the brain – while the fatty acids provide a ton of energy for growth. (This is why the fatty acids provide a ton of energy for growth. (This is why you often see a loss of fat accompanying a growth spurt.)you often see a loss of fat accompanying a growth spurt.)

• Too much or too little during childhood can result in Too much or too little during childhood can result in dwarfism or gigantism.dwarfism or gigantism.

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