Observations and Comments
1) The most important issue appears to be the cost of thyroid tests.
2) Two TSH and FT4 tests, five years apart, seems a very blunt measure of the natural history of thyroid function.
3) Elderly seems to be over 65.
4) They use the so common "without symptoms" definition of subclinical (hypo or hyper) but that, surely, depends on someone actually checking for symptoms? Which in turn implies knowing the symptoms.
5) Interesting that newly diagnosed atrial fibrillation is identified as a predictor of overt hypothyroidism. While so many patients feel it is used as an indicator of over-treatment.
6) The fact that in most people, TSH and FT4 remain stable over several years should not be a surprise. But using that to decide not to test in individuals is a questionable transfer of populations statistics to individuals. Again.
I am quite sure there are many more issues to be identified and discussed.
Repeat thyroid function tests for healthy older people are not needed
Published on 2 January 2019
doi: 10.3310/signal-000703
Older adults with normal thyroid function or subclinical thyroid dysfunction show notable long-term stability of their thyroid hormone levels. This suggests that it is safe for GPs not to routinely retest older adults unless they have risk factors or develop clinical symptoms of overt thyroid dysfunction.
Over five years, about 0.2% older adults with normal thyroid function will develop overt hypothyroidism and about 3.5% will develop subclinical hypothyroidism. Amongst those with subclinical hypothyroidism, about 2% will develop overt hypothyroidism.
The NIHR funded this study as there is a lack of consensus on the relevance of subclinical thyroid dysfunction and the need for repeat testing.
This could both reduce the burden of unnecessary repeat testing on patients and save the NHS resources.
discover.dc.nihr.ac.uk/cont...
Stability of thyroid function in older adults: the Birmingham Elderly Thyroid Study
Published on 28 August 2018
L Roberts, D McCahon, O Johnson, M S Haque, J Parle and R Hobbs
British Journal of General Practice , 2018
Background
Thyroid function tests (TFTs) are among the most requested tests internationally. However, testing practice is inconsistent, and potentially suboptimal and overly costly. The natural history of thyroid function remains poorly understood.
Aim
To establish the stability of thyroid function over time, and identify predictors of development of overt thyroid dysfunction.
Design and setting
Longitudinal follow-up in 19 general practices in the UK.
Method
A total of 2936 participants from the Birmingham Elderly Thyroid Study (BETS 1) with a baseline TFT result indicating euthyroid or subclinical state were re-tested after approximately 5 years. Change in thyroid-stimulating hormone (TSH), free thyroxine (FT4), and thyroid status between baseline and follow-up was determined. Predictors of progression to overt dysfunction were modelled.
Results
Participants contributed 12 919 person-years; 17 cases of overt thyroid dysfunction were identified, 13 having been classified at baseline as euthyroid and four as having subclinical thyroid dysfunction. Individuals with subclinical results at baseline were 10- and 16-fold more likely to develop overt hypothyroidism and hyperthyroidism, respectively, compared with euthyroid individuals. TSH and FT4 demonstrated significant stability over time, with 61% of participants having a repeat TSH concentration within 0.5 mIU/L of their original result. Predictors of overt hypothyroidism included new treatment with amiodarone (odds ratio [OR] 92.1), a new diagnosis of atrial fibrillation (OR 7.4), or renal disease (OR 4.8).
Conclusion
High stability of thyroid function demonstrated over the 5-year interval period should discourage repeat testing, especially when a euthyroid result is in the recent clinical record. Reduced repeat TFTs in older individuals is possible without conferring risk, and could result in significant cost savings.
discover.dc.nihr.ac.uk/cont...
Definitions used in the above study
An overactive thyroid (known as hyperthyroidism) is where the thyroid gland produces too much of the thyroid hormones. An underactive thyroid gland (hypothyroidism) is where your thyroid gland doesn't produce enough hormones.
Symptoms can vary, and a blood test measuring your hormone levels is the only accurate way to find out whether there's a problem. Thyroid function tests look at levels of thyroid-stimulating hormone (TSH) and thyroxine (T4) in the blood.
• A high level of TSH and a low level of T4 in the blood could mean you have an underactive thyroid.
• A low level of TSH and high levels of T3 and/or T4 usually means you have an overactive thyroid.
Your levels will be compared to what's normal for a healthy person.
• A high TSH and normal T4 without symptoms is referred to as subclinical hypothyroidism.
• A low TSH and normal T4 without symptoms is referred to as subclinical hyperthyroidism.
