Thyroid problems after 60 often look like something else entirely

Thyroid dysfunction becomes more common with age and harder to recognise, because the classic textbook presentations are largely descriptions of how it appears in younger people.

Hypothyroidism

Prevalence rises with age and is higher in women. The symptoms — fatigue, cold intolerance, weight gain, constipation, dry skin, hair thinning, low mood, slowed thinking — overlap almost completely with what people expect of getting older, which is why the diagnosis is often delayed.

Diagnosis is biochemical: raised TSH with low free T4 confirms overt hypothyroidism. Treatment with levothyroxine is straightforward, cheap and effective, and in older adults should start at a lower dose — typically 25 to 50 micrograms — and be titrated slowly, particularly where there is known coronary disease, because rapid correction can precipitate angina or arrhythmia.

Subclinical hypothyroidism, and the argument about it

This is where most of the disagreement sits. Subclinical hypothyroidism means a raised TSH with a normal free T4, and it is common — affecting perhaps 10 per cent of adults over 65, and more in women.

Two facts complicate it. First, the TSH reference range shifts upward with age; a TSH of 5.5 mIU/L in an eighty-five-year-old sits within the age-specific distribution and would be flagged as abnormal against a range derived largely from younger adults. Second, several studies have found that higher TSH in the very old is associated with better, not worse, survival.

The TRUST trial randomised adults over 65 with subclinical hypothyroidism to levothyroxine or placebo and found no improvement in symptoms or in tiredness. A parallel analysis in those over 80 found the same. That is a well-conducted negative result in exactly the population most likely to be treated.

Hyperthyroidism, which hides better

The classic picture — tremor, heat intolerance, anxiety, sweating, increased appetite, hyperactivity — is a young person's presentation.

In older adults, apathetic hyperthyroidism is common: weight loss, fatigue, low mood, withdrawal and weakness, without any of the adrenergic features. It is easily mistaken for depression or occult malignancy, and the correct diagnosis can be delayed for months.

The two findings that should prompt a thyroid function test in an older adult are unexplained atrial fibrillation and unexplained weight loss. Hyperthyroidism is a well-recognised precipitant of AF, and in some series accounts for a meaningful minority of new cases in this age group.

Untreated hyperthyroidism also accelerates bone loss and increases fracture risk, which is a particular concern where osteoporosis is already present.

Overtreatment with levothyroxine

Worth its own section, because it is common. A substantial proportion of long-term levothyroxine users have a suppressed TSH, meaning they are receiving more than they need.

The consequences of iatrogenic subclinical hyperthyroidism are not trivial in older adults: increased atrial fibrillation risk, accelerated bone loss, and in some cohort studies increased mortality.

Requirements fall with age as lean body mass declines, so a dose that was correct at fifty-five may be too high at eighty. Anyone on long-term levothyroxine should have TSH checked at least annually, and a suppressed result should prompt dose reduction rather than reassurance that everything is fine.

Absorption, which trips people up

Levothyroxine absorption is easily impaired. It should be taken on an empty stomach, ideally 30 to 60 minutes before food. Calcium supplements, iron, proton pump inhibitors, and coffee all reduce absorption meaningfully — coffee more than most people expect.

An unexplained rise in TSH in a stable patient is more often an absorption or adherence problem than a change in the thyroid, and is worth asking about before increasing the dose.

What about T3, and the desiccated preparations?

A proportion of patients on adequate levothyroxine continue to report symptoms, and combination T4/T3 therapy is frequently requested. Randomised trials have generally not shown consistent benefit over levothyroxine alone, though some patients report clear improvement and the debate remains genuinely live.

Desiccated thyroid extract is not recommended by major guidelines, principally because the T4:T3 ratio differs from human physiology and preparations vary in potency. In older adults, the higher T3 content raises particular concern about cardiac effects.

The practical summary

Test thyroid function in anyone with unexplained fatigue, cognitive change, low mood, weight loss or new atrial fibrillation. Repeat abnormal results before acting. Be cautious about treating mild subclinical hypothyroidism in the very old, where the evidence does not support benefit. And if you have been on the same levothyroxine dose for fifteen years, ask what your TSH actually is.