Endocrine Systems Use of Thyroid Hormone to Control Overall Metabolism

Endocrine Glands Ex. Insulin The endocrine system is made of glands and tissues that secrete hormones. Hormones are chemicals that influence metabolism of cells, the growth and development of body parts, and homeostasis. Hormones can be classified as peptides (proteins) or steroids (fats). Ex. Insulin Hormones are grouped by glands and chemical class in Table 20.1 on page 393.

The endocrine system This diagram shows the anatomical location of major endocrine glands in the body. The hypothalamus and pituitary gland are located in the brain, the thyroid and parathyroids are located in the neck, and the adrenal glands and pancreas are located in the pelvic cavity. The gonads include the ovaries in females, located in the pelvic cavity, and the testes in males, located outside this cavity in the scrotum. Also shown are the pineal gland, located in the brain, and the thymus, which lies ventral to the thorax.

Hypothalamus and the pituitary (Left) The hypothalamus produces two hormones, ADH and oxytocin, which are stored and secreted by the posterior pituitary. (Right) The hypothalamus controls the secretions of the anterior pituitary, and the anterior pituitary controls the secretions of the thyroid, adrenal cortex, and gonads, which are also endocrine glands.

Ex :Effects of Growth Hormone The quantity of GH is greatest during childhood and adolescence; GH promotes bone and muscle growth. Pituitary dwarfism results from too little GH during childhood. Giants result from too much growth hormone during childhood. If growth hormone is overproduced in an adult, it causes acromegaly. In acromegaly, since bone growth is no longer possible in adults, only the feet, hands and face (especially the chin, nose, and eyebrow ridges) can respond.

Effect of growth hormone The amount of growth hormone produced by the anterior pituitary during childhood affects the height of an individual. Plentiful growth hormone produces very tall basketball players. Too much growth hormone can lead to giantism, where insufficient amount results in limited stature and even pituitary dwarfism.

Acromegaly Acromegaly is caused by overproduction of GH in the adult. It is characterized by the enlargement of bones in the face, the fingers, and the toes as the person ages.

Thyroid Gland The thyroid gland is a large gland located in the neck, where it is attached to the trachea just below the larynx.

Thyroid Gland The thyroid gland requires iodine to produce thyroxine (T4) which contains four iodine atoms, and triiodothyronine (T3) which contains three iodine atoms. Thyroid hormones increase the metabolic rate, and stimulate all body cells to metabolize and use energy at a faster rate.

Effects of Thyroid Hormones If iodine is lacking in the diet, a simple goiter develops. Use of iodized salt helps prevent simple goiters. Hypothyroidism in childhood produces cretinism; in adulthood it causes myxedema. If the thyroid is overactive (Grave’s disease) an exophthalmic goiter develops a type of Hyperthyroidism. Individuals with cretinism are short and stocky, and mental retardation can result unless thyroid hormone therapy is begun early. Hypothyroidism in adults causes myxedema, which is characterized by lethargy, weight gain, loss of hair, slower pulse rate, lowered body temperature, and thickness and puffiness of the skin.

HYPOTHRYROIDISM Slow Heart Rate Cold Intolerance

HYPERTHYROIDISM