CALCIFEROL
The tendons of the sole of the foot are
fixed under the calcaneus, and the asso-
ciated
muscles
are
important
in
supporting
the
arches
of the
foot.
Inflammation around these tendons (as
occurs in plantar
fasciitis
)
causes pain
and tenderness under the heel when
standing or walking. A calcaneal spur (a
bony protrusion) occurs in some peo-
ple
with
plantar
fasciitis
and
also,
occasionally, in those with healthy feet.
calciferol
A former name for vitamin D 2.This vit-
amin is now more commonly known
as ergocalciferol (see
vitamin
D).
calcification
The deposition of
calcium
salts in body
tissues. Calcification is part of the nor-
mal
processes
of
bone
and
teeth
formation and the healing of fractures.
It also occurs in injured muscles, in
arteries affected by
atherosclerosis,
and
when blood calcium levels are raised by
disorders of the
parathyroid glands
.
calcification, dental
The deposition of
calcium
salts in devel-
oping teeth. Primary teeth (see
eruption
of teeth
)
begin to calcify in a fetus at
between three and six months gesta-
tion. Calcification of permanent teeth
(other than the wisdom teeth) begins
between birth and four years.
Certain tooth conditions can cause
abnormal calcification. In amelogenesis
imperfecta,
an enamel disorder
(see
hypoplasia, enamel
) ,
teeth have a thin,
grooved covering due to incomplete
calcification. Another cause is absorp-
tion of high levels of fluoride
(see
fluorosis
) and drugs, such as
tetracycline
,
that are taken in pregnancy.
calcinosis
The abnormal deposition of
calcium
salts
in the skin, muscles, or
connective tissues,
forming
nodules
.
Calcinosis occurs in
connective tissue disorders such as
scle-
roderma
.
(See also
calcification.
)
calcipotriol
A derivative of
vitamin D
that is used in
topical treatments for the skin condi-
tion
psoriasis
.
calcitonin
A
hormone
produced by the
thyroid
gland
that helps to control blood
cal-
cium
levels by slowing the rate at w hich
calcium is lost from the bones.
WHY IT IS USED
A synthetic form of calcitonin used
in the treatment of
Paget’s disease
,
in
w hich the bones grow abnormally and
become deformed, causing pain and an
increased risk of fracture. Injections of
calcitonin can generally halt abnormal
bone formation in about a week and
can relieve pain w ithin a few months.
Calcitonin is also used in the treat-
ment
of
hypercalcaemia
(abnormally
high levels of calcium in the blood),
w hich may be caused by overactivity of
the
parathyroid glands
or by
bone cancer
.
It helps to relieve the nausea and vom-
iting that result from hypercalcaemia
by rapidly reducing the level of calcium
circulating in the blood.
SIDE EFFECTS
Calcitonin causes m inim al side effects.
Gastrointestinal reactions, such as nau-
sea, vomiting, and diarrhoea, usually
dim inish with continued use.
calcium
The body’s most abundant mineral, cal-
cium
is
essential
for
cell
function,
muscle contraction, the transmission of
nerve impulses from nerve endings to
muscle fibres, and for
blood clotting
.
Calcium phosphate is the hard, basic
constituent of teeth and bones. Dietary
sources of calcium include dairy prod-
ucts, eggs, and green, leafy vegetables.
CONTROL OF CALCIUM LEVELS
Vitamin D
and certain hormones help to
control the overall amount of calcium
in the body. They act by regulating the
amount of calcium that is absorbed
from food and the amount filtered out
from the blood by the kidneys and
excreted in the urine.
The levels of calcium in the blood are
controlled by the actions of two hor-
mones: parathyroid hormone, w hich is
produced by the
parathyroid glands
,
and
calcitonin
,
w hich is produced by the
thyroid gland. W hen the level of cal-
cium in the blood falls to a low level,
the parathyroid glands release more
parathyroid hormone, w hich raises the
blood
calcium
level
by
helping
to
release
calcium
from
the
enormous
reservoir in the bones. W hen the blood
calcium level rises significantly, the thy-
roid gland releases more calcitonin.
This hormone counteracts the effects of
parathyroid hormone, thereby lower-
ing the level of calcium in the blood.
DISORDERS OF CALCIUM METABOLISM
Abnormally high levels of calcium in
the blood
(
hypercalcaemia
)
or abnor-
mally low levels
(
hypocalcaemia
)
may
seriously disrupt cell function, particu-
larly in muscles and nerves. (See also
mineral supplements.
)
calcium carbonate
A
calcium
salt used in some
antacid
drugs
,
w hich can be taken for the treat-
ment of indigestion.
calcium channel blockers
COMMON DRUGS
•Amlodipine • Diltiazem •Felodipine
• Isradipine •Lacidipine •Lercanidipine
• Nicardipine • Nifedipine •Verapamil
Drugs used in the treatment of
angina
pectoris
(chest pain due to impaired
blood supply to the heart muscle),
hypertension
(high blood pressure), and
certain
types
of
cardiac
arrhythmia
(irregular heartbeat).
HOW THEY WORK
Calcium
channel
blockers
work
by
interfering with the movement of
cal-
cium
across the membranes of muscle
cells in blood vessels and in the heart
muscle itself. This action decreases the
work of the heart in pumping blood,
reduces the pressure of blood flow
through the body, and improves blood
circulation through the heart muscle.
The drugs also slow the passage of
nerve impulses through the heart’s in -
ternal conduction system, w hich helps
to correct certain types of arrhythmia.
SIDE EFFECTS
The side effects of calcium
channel
blockers are mainly related to their
action of increasing the blood flow
through tissues. These effects include
headaches,
swollen
ankles,
flushing,
and dizziness. Adverse effects tend to
dim inish w ith continued treatment.
calculus
A hard deposit in the body. Calculus
may form on the surface of the teeth
(see
calculus, dental
) .
Alternatively,
it
may be a small, hard, crystalline mass
that forms in a body cavity from certain
substances in fluids such as bile, urine,
or
saliva.
Such
calculi
(also
called
stones)
can occur in the gallbladder
and bile ducts (see
gallstones
), kidneys,
ureters,
bladder
(see
calculus, urinary
tract
), or in the salivary ducts.
Although some calculi do not cause
any symptoms, some can cause severe
pain, in w hich case they may need to
be dissolved, shattered,
or surgically
removed from the body cavity.
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