reabsorption and increasing serum calcium. Parathormone also acts on the kidneys to
increase calcium reabsorption and on the intestinal tract to increase the absorption of
calcium. The net effect is an increase in serum calcium level.
b. Diseases Involving the Parathyroid Glands.
(1) Hypoparathyroidism. Hypoparathyroidism is a disease usually caused
by inadvertent surgical removal of the parathyroid glands. This removal results in a lack
of parathromone that decreases the serum calcium. Lowering the serum calcium level
causes increased neuromuscular irritability that results in tetany. Tetany is
characterized by intermittent muscular contractions, tremor, and muscular pain.
(2) Hyperparathyroidism. Occasionally, the parathyroid glands
produce too much parathormone. This condition is called hyperparathyroidism.
Hyperparathyroidism causes erosion of the skeletal muscle system. Such an erosion
results in weak, painful, and brittle bones.
c. Calcitonin. Calcitonin apparently performs as a sort of fine control of the
blood's calcium level. Its action is essentially the reverse of parathormone. Calcitonin
causes the body to build more bone-thus decreasing the serum calcium level.
Calcitonin is produced by both parathyroid and thyroid glands.
6-10. THE ADRENAL GLANDS
The adrenal glands (also known as suprarenal glands) are embedded in the fat
above each kidney. Both adrenal glands have an internal medulla and an external
a. Hormones of the Adrenal Medulla. The medullary (inside the gland) portion
of each adrenal gland produces a pair of hormones, epinephrine (adrenalin) and
norepinephrine (noradrenalin). These hormones are both involved in the mobilization of
energy during the stress reaction ("fight or flight" response). These hormones are also
produced in the autonomic nervous system. Therefore, production of these hormones
in the adrenal medulla is not necessary for life. After production, these hormones are
stored in the adrenal medulla and are released in large quantities during the stress
(1) Epinephrine (adrenalin). Epinephrine has the following effects on the
body, constriction of arterioles which produces a rise in blood pressure, increased heart
rate and force of contraction, inhibition of intestinal activity, contraction of the
gallbladder, dilation of the pupils, stimulation of glycogenolysis, stimulation of
adrenocorticotropic hormone (ACTH) production, and bronchodilation.
(2) Norepinephrine (noradrenalin). Norepinephrine has less an effect on the
gastrointestinal tract and a greater effect on blood pressure than does epinephrine.
Norepinephrine has no effect on the bronchioles. Tumors of the adrenal medulla are