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.