Levothyroxine Therapy in Elderly Patients with Hypothyroidism
Frontiers in Endocrinology: Published on March 2021
Hypothyroidism is a common
condition caused by thyroid hormone deficiency.
The prevalence of hypothyroidism
increases with age and subclinical hypothyroidism affects up to 15% of adults
65 years of age or older.
Levothyroxine (L-T4) treatment of
overt hypothyroidism can be more challenging in the elderly compared to young
patients.
Elderly people have more comorbidity
compared to young patients, complicating correct diagnosis and management of
hypothyroidism.
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Cardiovascular complications pose a
significant challenge in determining the appropriate dosage and titration of
L-T4 in hypothyroidism due to the higher risk of cardiac ischemia and
dysfunction. To prevent cardiac incidents, the maintenance dose may need to be
lower.
However, it is worth noting that
L-T4 has a positive effect on cardiac function by improving performance.
Therefore, the presence of cardiac ischemia should not deter the administration
of L-T4.
Endocrinologists have a
responsibility to collaborate with cardiologists to implement prophylactic
cardiac measures, such as invasive cardiac surgery or medical therapy, to
address cardiac ischemic angina.
Managing mild (subclinical)
hypothyroidism in the elderly is even more complex due to the prevalence of
comorbidities. These comorbidities can mimic mild hypothyroidism both
clinically and biochemically, making correct diagnosis challenging.
Other cases of hypothyroidism,
including medication-induced, iodine overload, or
hypothalamus-pituitary-hypothyroidism, present specific challenges in
management, and these cases are more commonly observed in the elderly
population.
Regularly measuring thyroid
hormones at individually tailored intervals is crucial to avoid over-treatment,
which can lead to an increased risk of cardiac morbidity and mortality,
osteoporosis, cognitive dysfunction, and muscle deficiency.
Indication for Levothyroxine
Treatment of Hypothyroidism in Elderly
The indication for L-T4 treatment
of overt hypothyroidism is similar in young and elderly hypothyroid patients.
However, more caution must be paid to a variety of the complicating factors
that are more prevalent with increasing age.
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Firstly, a correct diagnosis is
more complicated due to the much possible comorbidity that can give rise to a
falsely elevated serum TSH concentration even above 10 mU/L as required for the
diagnosis of overt hypothyroidism.
A complimentary measurement of fT4
estimate must be done in all cases, while measurement of serum T3 is not
recommended for the treatment indication of hypothyroidism.
Both diagnosing and decision of
treatment or not are much more difficult in patients with mild or subclinical
hypothyroidism in the elderly for a variety of reasons.
Hypothyroidism has a profoundly
negative effect on cardiac performance which results in low exercise
performance, and more prominently so in elderly patients. This is particularly
the case in patients with a pre-existing heart failure, which should always be
considered a possibility in the evaluation of older patients with hypothyroidism.
Even in asymptomatic individuals it
is therefore pertinent to perform a very rigorous assessment of elderly
hypothyroid patients before commencement of L-T4 therapy in order to avoid
provoking cardiac ischemia and/or insufficiency by increasing the resting
metabolic rate.
In case of very high age and/or
suspicion of a cardiac condition the patient may require a stress test or
coronary angiography to aid in the risk assessment.
In case of any cardiac issues it is
wise to consult a cardiologist also to discuss possible relevant prophylactic
treatment options, to open the vessels surgically in case of stenosis or by
antianginous medications.
It is also sometimes prudent to
start levothyroxine therapy in patients with cardiac conditions during
hospitalization and monitoring of cardiac rhythm and function.
It is important to realize that normal thyroid function and thus also
L-T4 therapy of overt hypothyroidism is eventually beneficial for cardiac
function, so it is clinically imperative to make an effort to persuade the
patient to comply with the treatment even if there are obstacles to starting
the therapy.
The frailty status is another
important factor to consider before initiation of LT4 treatment of elderly
people with subclinical hypothyroidism.
The frail elderly are
vulnerable to drugs side effects, overtreatment and poor compliance.
A conservative wait-and-see
approach for frail older patients even in the presence of thyroid autoimmunity.
Due to the vague symptoms of
subclinical hypothyroidism also in the elderly, the diagnosis is often suggested
by incidental discovery of a high TSH within a package of blood measurements in
persons showing up at the general practitioner for being tired.
If deciding on performing a
therapeutic trial together with the patient, proper treatment monitoring and
particularly avoiding overdosing is extremely important not to put the patient
at risk.
Once a patient-clinician agreement
on initiating levothyroxine treatment has been reached, three main issues are
particularly relevant in the elderly patient, in order to ensure appropriate
treatment:
Is cardiac comorbidity present?
How should treatment be initiated?
What is the treatment target to aim for?
In case cardiac co-morbidity has
been ruled out, possibly in collaboration with a cardiology expert, it seems
safe to start similarly as in younger patients ; nonetheless, most
clinicians start at lower doses and up-titrate at a slower pace, acknowledging
the general frailty of this age-group.
Lacking good evidence the treatment
target is mostly empirically based and could be either (a) TSH (ideally related
to an age specific reference range), (b) other biochemical and clinical indices
of thyroid function or (c) patient-experienced variables, e.g.,
thyroid-related patient-reported outcomes.
Blood-lipids are frequently monitored during L-T4 therapy as
indication of treatment effect.
Apart from titrating L-T4 to an
appropriate biochemical target, a
classical patient-physician encounter in terms of the physician inquiring
about symptoms of over-replacement as part of a clinical interview is paramount
for proper management.
It seems prudent to aim for fT4 in the lower half of the reference range
in older patients, paying attention to lipids and body mass index, and
closely monitoring symptoms and signs of overtreatment.
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