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P A R T 6
Drugs acting on the endocrine system
T
his chapter reviews drugs that are used to affect the
function of the thyroid and parathyroid glands. These
two glands are closely situated in the middle of the neck
and share a common goal of calcium homeostasis. Serum
calcium levels need to be maintained within a narrow
range to promote effective blood coagulation, as well as
nerve and muscle function. In most respects, however,
these glands are very different in structure and function.
THE THYROID GLAND
The thyroid gland is located in the middle of the neck,
where it surrounds the trachea like a shield (Figure 37.1).
Its name comes from the Greek words
thyros
(shield)
and
eidos
(gland). It produces two hormones—thyroid
hormone and calcitonin.
Structure and function
The thyroid is a vascular gland with two lobes—one on
each side of the trachea—and a small isthmus connect-
ing the lobes. The gland is made up of cells arranged in
circular
follicles
. The centre of each follicle is composed
of colloid tissue, in which the thyroid hormones
produced by the gland are stored. Cells found around
the follicle of the thyroid gland are called parafollicu-
lar cells (see Figure 37.1). These cells produce another
hormone,
calcitonin
, which affects calcium levels and
THYROID AGENTS
Thyroid hormones
liothyronine
thyroxine
Antithyroid agents
Thioamides
carbimazole
propylthiouracil
Iodine Solutions
sodium iodide
131
I
strong iodine solution,
potassium iodide
PARATHYROID AGENTS
Antihypocalcaemic agents
calcitriol
teriparatide
Antihypercalcaemic agents
Bisphosphonates
alendronate
clodronate
etidronate
ibandronate
pamidronate
risedronate
tiludronate
zoledronic acid
Calcitonins
calcimimetic
calcitonin salmon
(salcitonin)
cinacalcet
Thyroid replacement
hormone replaces
hormones from colloid
when levels are low
Parathyroid glands
Thyroid
follicles
Blood vessel
Thioamides,
iodines work
here
Colloid
Parafollicular cells
Thyroid cells
Trachea
Thyroid gland
FIGURE 37.1
The thyroid and
parathyroid glands. The basic unit
of the thyroid gland is the follicle.
