Very sadly, only a small fragment of this paper is available to we mortals. So we really don't know what it says.
Interestingly, a superficial reading suggests that the professor laments labs only doing TSH and not FT4 and FT3.
BMJ. 2013 Nov 20;347:f6842. doi: 10.1136/bmj.f6842.
Investigating low thyroid stimulating hormone (TSH) level.
Department of Human Metabolism, Faculty of Medicine, Dentistry and Health, University of Sheffield, Sheffield S10 2HQ, UK.
The commonest causes of a low serum level of thyroid stimulating hormone (TSH) are excessive levothyroxine replacement, non-thyroidal illness, and subclinical hyperthyroidism.
In a patient who is not taking levothyroxine treatment, a low TSH level should prompt measurement of free thyroxine (FT4) and free triiodothyronine (FT3). If these are normal, the TSH level should be measured after six weeks to rule out non-thyroidal illness.
Subclinical hyperthyroidism is common in elderly people, and treatment may be indicated before progression to overt thyrotoxicosis to minimise bone loss and risk of atrial fibrillation