gland to stimulate the release of its hormones and to help regulate body temperature (fig. 1-47). PITUITARY GLAND The pituitary is a small, pea-sized gland located at the base of the brain in the sella turcica, the saddle-shape depression of the sphenoid bone (fig. 1-47). It is often called the master gland of the body because it influences many other endocrine glands. Although the pituitary looks like just one gland, it actually consists of two separate glands, the anterior pituitary gland and the posterior pituitary gland. Anterior Pituitary Gland The anterior pituitary gland plays the more important role in influencing body functions. The hormones produced by the anterior pituitary gland have a broad and significant range of effects. SOMATOTROPIN.—Somatotropin, the growth hormone, influences body growth and development. During the growth years, an overproduction of somatotropin causes giantism, while the lack of it causes dwarfism. An overproduction after the growth years causes acromegaly, which is characterized by the development of abnormally large hands, feet, and jaw. T H Y R O T R O P I N . — T h y r o t r o p i n , o r t h e thyroid-stimulating hormone (TSH), influences the growth, development, and secreting activities of the thyroid gland. GONADOTROPIN.—Gonadotropin influences the gonads and is essential for the normal development and functioning of both male and female reproductive systems. A D R E N O C O R T I C O T R O P I N . — T h e adrenocorticotropin hormone (ACTH) acts primarily on the adrenal cortex (the outer portion of the adrenal glands), stimulating its growth and its secretion of corticosteroids. Corticosteroid hormones affect every cell in the body and are discussed in more detail later in this section. Posterior Pituitary Gland The posterior pituitary gland produces two hormones, antidiuretic hormone (ADH) and oxytocin. A N T I D I U R E T I C . — T h e A D H h o r m o n e , promotes the conservation of water by the kidney. When ADH is not produced in adequate amounts, the daily urine volume is between 10 and 15 liters instead of the normal 1.5 liters. This condition is known as diabetes insipidus. OXYTOCIN.—Oxytocin stimulates contraction of the muscles of the uterus, particularly during pregnancy. It also plays an important role in the production of milk in the mammary glands of nursing mothers. THYROID GLAND The thyroid gland, shaped like a butterfly, lies in the anterior part of the neck, below the larynx (fig. 1-47). It consists of two lobes, one on each side of the upper trachea, connected by a strip of tissue called the isthmus. The thyroid secretes the iodine containing hormone thyroxin, which controls the rate of cell metabolism. Excessive secretion of thyroxin raises the metabolic rate and causes hyperthyroidism. This condition is characterized by a fast pulse rate, dizziness, increased basal metabolism, profuse sweating, tremors, nervousness, and a tremendous appetite coupled with a loss of weight. 1-42 HM3F0147 HYPOTHALAMUS PITUITARY GLAND PARATHYROID GLAND THYROID GLAND KIDNEY PANCREAS ADRENAL GLAND OVARY (IN FEMALE) TESTIS (IN MALE) Figure 1-47.—Major endocrine glands.