DRUGS ACTING ON THE THYROID GLAND : HYPOTHYROIDISM
CLASSIFICATION
DRUGS
PHARMACODYNAMICS
PHARMACOKINETICS
INDICATIONS
SIDE EFFECTS /
INTERACTIONS
NURSING
CONSIDERATIONS
THYROID
REPLACEMENTS
 LEVOTHYROID
Converts to T3, then binds to
Variable, incomplete absorption Hypothyroidism PO:
thyroid receptor proteins exerting from GI tract. Protein binding:
 ADULTS
metabolic effects through control greater than 99%. Widely
60 YRS OR
of DNA transcription and protein distributed. Deiodinated in
YOUNGER
synthesis. Therapeutic Effect:
peripheral tissues, minimal
WITHOUT
Involved in normal metabolism, metabolism in liver. Eliminated
EVIDENCE
growth and development. Increases by biliary excretion. Half-life: 6–
OF
basal metabolic rate, enhances
7 days.
CORONAR
gluconeogenesis, stimulates protein
Y HEART
synthesis
DISEASE:
1.6
mcg/kg/day
as single
daily dose.
Adjust dose
by 12.5–25
mcg/day
q3–6 wks.
Usual
maintenanc
e: 100–125
mcg/day.

ADULTS
OLDER
THAN 60
YRS
WITHOUT
EVIDENCE
OF


Occasional:
Reversible hair
loss at start of
therapy in
children. Rare:
Dry skin, GI
intolerance,
rash, urticarial,
pseudotumor
cerebri, severe
headache in
children
Excessive
dosage
produces
signs/symptom
s of
hyperthyroidis
m (weight
loss,
palpitations,
increased
appetite,
tremors,
anxiety,
tachycardia,
hypertension,
headache,
insomnia,
menstrual


BASELINE
ASSESSMENT
Obtain baseline TSH,
T3, T4, weight, vital
signs.
Signs/symptoms of
diabetes, diabetes
insipidus, adrenal
insufficiency, and
hypopituitarism may
become intensified.
Treat with
adrenocortical
steroids before
thyroid therapy in
coexisting
hypothyroidism and
hypoadrenalism.
INTERVENTION/E
VALUATION
Monitor pulse for
rate, rhythm (report
pulse greater than
100 or marked
increase). Observe
for tremors, anxiety.
Assess appetite, sleep
pattern. Children:
(Undertreatment):
May decrease
CORONAR
Y HEART
DISEASE:
Initially,
25–50 mcg
once daily.


ADULTS
WITH
CARDIAC
DISEASE:
Initially,
12.5–50
mcg/day.
Adjust dose
by 12.5– 25
mcg/day at
6–8-wk
intervals.
CHILDRE
N OLDER
THAN 12
YRS,
GROWTH
AND
PUBERTY
INCOMPL
ETE: 2–3
mcg/kg/day.
CHILDRE
N 6–12
YRS: 4–5
mcg/kg/day.
CHILDRE
N 1–5 YRS:
5–6
mcg/kg/day.
CHILDRE
N 6–12
MOS: 6–8
mcg/kg/day.
CHILDRE
N 3–5
MOS: 8–10
irregularities).
Cardiac
arrhythmias
occur rarely.
Long-term
therapy may
decrease bone
mineral
density

intellectual
development, linear
growth.
(Overtreatment):
Adversely affects
brain maturation,
accelerates bone age.
Monitor thyroid
function tests.
PATIENT/ FAMILY
TEACHING • Do not
discontinue drug
therapy; replacement
for hypothyroidism is
lifelong. • Follow-up
office visits, thyroid
function tests are
essential. • Take
medication at the
same time each day,
preferably in the
morning. • Monitor
pulse for rate,
rhythm; report
irregular rhythm or
pulse rate over 100
beats/ min. •
promptly report chest
pain, weight loss,
anxiety, tremors,
insomnia. • Children
may have reversible
hair loss, increased
aggressiveness
during first few mos
of therapy. • Full
therapeutic effect
may take 1–3 wks.
mcg/kg/day.




LIOTHYRONINE

In hormonal
replacement,
liothyronine is more
potent and present a
faster action when
Liothyronine replaces
endogenous thyroid hormone
and then exerts its physiologic
effects by controlling DNA
transcription and protein
CHILDRE
N
YOUNGER
THAN 3
MOS: 10–
15
mcg/kg/day.
Myxedema
Coma IV:
ADULTS,
ELDERLY:
Initially,
200–400
mcg, then
50–100 mcg
once daily
until able to
tolerate PO
administratio
n. Pituitary
ThyroidStimulating
Hormone
(TSH)
Suppression
PO:
ADULTS,
ELDERLY:
Doses greater
than 2
mcg/kg/day
usually
required to
suppress
TSH below
0.1
milliunits/L.
Thyroid

supplementation in
hypothyroidism. 
Treatment or
suppression of
weight loss
nervousness

Monitor and report
signs of excessive or
inadequate dosing.
compared to
synthesis. This effect on DNA euthyroid goiters. 
levothyroxine but the is obtained by the binding of Diagnostic agent

time of action is
liothyronine to the thyroid
for suppression
significantly shorter. receptors attached to DNA.
tests to differentiate

The type of treatment Exogenous liothyronine exerts mild
needs to be well
all the normal effects of the hyperthyroidism
evaluated as the fast
endogenous thyroid T3
from thyroid gland
correction of thyroid hormone. Hence, it increases autonomy.
hormones in certain
energy expenditure,
Treatment of
diseases presents
accelerates the rate of cellular myxedema coma
additional risks such as oxidation stimulating growth, (IV formulation).
heart failure.3 The onset maturation, and metabolism of
of activity is observed a the body tissues, aids in
few hours after
myelination of nerves and
administration and the development of synaptic
maximum effect is
processes in the nervous
observed after 2-3 days. system and enhances
carbohydrate and protein
metabolism
excessive sweating
Excessive doses
mimic
sensitivity to heat
hyperthyroidism, as
indicated by
nervousness, weight
loss, muscle wasting,
tachycardia, and heat
intolerance.
Inadequate doses
mimic
temporary hair
loss (particularly
in children during
the first months of
therapy)

hypothyroidism, as
indicated by
lethargy, weight
gain, bradycardia,
and cold intolerance.
Assess heart rate,
ECG, and heart
sounds, especially
during exercise
(See Appendices
G, H). Report any
rhythm disturbances
or symptoms of
increased
arrhythmias,
including
palpitations, chest
discomfort,
shortness of breath,
fainting, and
fatigue/weakness.

Assess episodes of
angina pectoris at
rest and during
exercise. Attempt to
determine if pain is
drug related, or
caused by
cardiovascular
dysfunction (e.g.,
angina that occurs
during exercise).


Assess height in
children
periodically; inform
physician of delayed
growth that might
indicate premature
skeletal maturation
and closure of
epiphyseal plates.
Monitor and report
signs of CNS
toxicity, including
irritability and sleep
loss. Sustained or
severe CNS signs
are typically
consistent with
hyperthyroidism and
may require an
adjustment in drug
dose.
 LIOTRIX
Thyroid hormone drugs are
The hormones, T4 and T3, are May be used to
fatigue, sluggishness,
natural or synthetic preparations tyrosine-based hormones
treat primary,
containing T4 or T3 or both.
produced by the thyroid gland. secondary or
increase in weight,
T4 and T3 are produced in the Iodine is an important
tertiary
alopecia, palpitations,
human thyroid gland by the
component in their synthesis. hypothyroidism.
iodination and coupling of the The major secreted form of
May also be used to dry skin, urticaria,
amino acid tyrosine. Liotrix is a thyroid hormone is T4. T4 is suppress thyroid
headache,
synthetic preparation of T4 and converted T3, the more active stimulating
hyperhidrosis,
T3 in a 4:1 weight-based ratio. thyroid hormone, by
hormone (TSH)
These hormones enhance
deiodinases in peripheral
secretion in patients pruritus, asthenia,
oxygen consumption by most tissues. T3 acts in the body to with simple
increased blood
tissues of the body and increase increase basal metabolic rate, (nontoxic) goiter,
the basal metabolic rate and the alter protein synthesis and
subacute or chronic pressure, arthralgia,
metabolism of carbohydrates, increase the body's sensitivity lymphocytic
myalgia, tremor,
lipids and proteins. Thus, they to catecholamines (such as
thyroiditis
hypothyroidism,
exert a profound influence on adrenaline). Thyroid hormones multinodular goiter,
increase in TSH,
every organ system in the body are essential for proper
and in the
and are of particular importance development and
management of
decrease in TSH,
in the development of the
differentiation of all cells of thyroid cancer.
nausea, chest pain,
central nervous system.
the human body. T4 and
May be used in
T3 regulate protein, fat and
conjunction with hypersensitivity,
carbohydrate metabolism to other antithyroid
keratoconjunctivitis
varying extents. The most
agents to treat
pronounced effect of the
thyrotoxicosis to sicca, increased heart
hormones is in altering how prevent
rate, irregular heart
human cells use energetic
goitrogenesis and
rate, anxiety,
compounds. The thyroid
hypothyroidism.
hormone derivatives bind to May also be used depression, and
the thyroid hormone receptors for differential
insomnia.
initially to initiate their
diagnosis of
downstream effects.
suspected mild
hyperthyroidism or
thyroid gland
autonomy.
Thyroid hormones should
be used with great caution
in a number of
circumstances where the
integrity of
the cardiovascular system,
particularly the coronary
arteries, is suspected. These
include patients with angina
pectoris or the elderly, in
whom there is a greater
likelihood of occult cardiac
disease. In these patients
therapy should be initiated
with low doses, i.e., one
tablet of Thyrolar (liotrix) %
or Thyrolar (liotrix) %.
When, in such patients, a
euthyroid state can only be
reached at the expense of an
aggravation of
the cardiovascular disease,
thyroid hormone dosage
should be reduced.
Thyroid hormone therapy in
patients with
concomitant diabetes
mellitus or diabetes insipidu
s or
adrenal cortical insufficienc
y aggravates the intensity of
their symptoms.
Appropriate adjustments of
the various therapeutic
measures directed at these
concomitant endocrine
diseases are required.
 THYROID
DESICCATED
Desiccated thyroid treats
hypothyroidism (low
thyroid hormone). Desiccated
thyroid is also used to treat or
prevent goiter (enlarged thyroid
gland), and is also given as part
of a medical tests for thyroid
disorders.
Thyroxine (T4): 40% to 80%;
T3: 95%; desiccated thyroid
contains T4, T3, and iodine
(primarily bound). Hepatic to
triiodothyronine (active);
~80% T4 deiodinated in
kidney and periphery;
glucuronidation/conjugation
also occurs; undergoes
enterohepatic recirculation
Initial dose: 30 mg

orally per day 
Maintenance dose:

Increase in
increments of 15
mg per day every 2
to 3 weeks to a 
usual maintenance

dose of 60 to 120

mg/day

Fast heart rate
Hair loss
Muscle pain
Irregular heartbeats
(arrhythmias)
Nervousness
Tremor
Diarrhea
Cramps


Thyroid desiccated
is generally
acceptable for use
during pregnancy.
Controlled studies in
pregnant women
show no evidence of
fetal risk.
Adrenal
insufficiency: Use
with caution in
patients with adrenal
insufficiency;
symptoms may be
exaggerated or
aggravated;
contraindicated in
patients with
uncorrected adrenal
insufficiency.
Treatment with
glucocorticoids
should precede
thyroid replacement
therapy in patients
with adrenal



insufficiency
(ATA/AACE
[Garber 2012]).
Cardiovascular
disease: Use with
caution and reduce
dosage in patients
with angina pectoris
or other
cardiovascular
disease; chronic
hypothyroidism
predisposes patients
to coronary artery
disease.
Diabetes: Use with
caution in patients
with diabetes
mellitus and
insipidus; symptoms
may be exaggerated
or aggravated.
Myxedema: Use
with caution in
patients with
myxedema;
symptoms may be
exaggerated or
aggravated; initial
dosage reduction is
recommended in
patients with longstanding myxedema.