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. THYROTROPIN,  or  the  thyroid-stimulating hormone  (TSH),  influences  the  growth,  develop- ment, and secreting activities of the thyroid gland. GONADOTROPIN   influences   the   gonads (ovaries or testes) and is essential for the normal development  and  functioning  of  both  male  and female  reproductive  systems. The   ADRENOCORTICOTROPIC   hormone (ACTH)  acts  primarily  on  the  adrenal  cortex, stimulating  its  growth  and  its  secretion  of  cor- ticosteroids.  Removal  of  the  pituitary  leads  to rapid  atrophy  of  the  adrenal  cortex. The  posterior  lobe  of  the  pituitary  produces at least two hormones, vasopressin and oxytocin. VASOPRESSIN acts as an antidiuretic hormone (ADH),  promoting  the  conservation  of  water  by the  kidney.  When  ADH  is  not  produced  in  ade- quate  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  stimulates  contraction  of  the muscles  of  the  uterus,  particularly  during  preg- nancy. It also plays an important role in the pro- duction of milk in the mammary glands of nurs- ing  mothers. THYROID   GLAND The thyroid, shaped like a butterfly, lies in the anterior part of the neck, below the larynx. It con- sists of two lobes, one on each side of the upper trachea, connected by a strip of tissue called the isthmus. The thyroid secretes the iodinecontain- ing   hormone   THYROXIN,   which   controls   the rate  of  cell  metabolism.  Excessive  secretion  of thyroxin  raises  the  metabolic  rate  and  causes hyperthyroidism,  a  condition  characterized  by  a fast  pulse  rate,  dizziness,  increased  basal metabolism,   profuse   sweating,   tremors,   ner- vousness, and a tremendous appetite yet a loss of weight.  The  thyroid  may  become  enlarged. Iodine  is  essential  for  the  formation  of  thy- roxin. To prevent simple goiter, iodine-containing foods,  such  as  vegetables,  iodized  salt,  and seafood,  are  eaten. Hypothyroidism, on the other hand, is caused by an insufficient secretion of thyroxin. The pa- tient  exhibits  a  decrease  in  basal  metabolism,  and sweating  is  almost  absent.  There  may  be  a  weight gain and constant fatigue. The heart rate may be slow,  and  there  may  be  an  enlargement  of  the gland, called a simple goiter. There may also be personality   changes   characterized   by   slow, lethargic mental functioning. Hypothyroidism in an infant may result in cretinism with impaired mental  and  physical  development. PARATHYROID   GLANDS Parathyroid  glands  are  four  small  round bodies located just posterior to the thyroid gland. Their   hormone,   PARATHORMONE,   regulates the calcium and phosphorus content of the blood and  bones.  The  amount  of  calcium  is  important in  certain  tissue  activities,  such  as  bone  forma- tion,  coagulation  of  blood,  maintenance  of  nor- mal  muscular  excitability,  and  milk  production in  the  nursing  mother.  Diminished  function  or removal  of  the  parathyroid  glands  results  in  a  low calcium level in the blood, and in extreme cases death may occur, preceded by strong contraction of  the  muscles  (tetany)  and  convulsions. Hyperparathyroidism,  an  excess  of  parathy- roid hormone in the blood, causes calcium levels in  the  blood  to  become  elevated  by  the  withdrawal of  calcium  from  the  bones,  leaving  the  skeleton demineralized  and  subject  to  spontaneous  frac- tures.  The  excess  calcium  may  be  deposited  as stones in the kidneys. ADRENAL   GLANDS The adrenal glands are located on the superior surface  of  each  kidney,  fitting  like  a  cap.  They consist  of  an  outer  portion,  the  cortex,  and  an inner  portion,  the  medulla. Adrenal Cortex Specialized  cells  in  the  outer  layer  of  the adrenal cortex produce three types of steroid hor- mones  that  are  of  vital  importance. MINERALOCORTICOIDS  are  regulators  of fluid  and  electrolyte  balance.  They  are  sometimes called   salt   and   water   hormone   because   they regulate the excretion and absorption of sodium, chlorine,  potassium,  and  water. GLUCOCORTICOIDS   are   essential   to metabolism. They increase certain liver functions and have an anti-inflammatory effect. Clinically they  are  used  to  suppress  inflammatory  reactions, to   promote   healing,   and   to   treat   rheumatoid arthritis. 3-41