Editorials

Thyroid function tests and hypothyroidism

BMJ 2003; 326 doi: https://doi.org/10.1136/bmj.326.7384.295 (Published 08 February 2003) Cite this as: BMJ 2003;326:295

AUTOIMMUNE HYPOTHYROIDISM AND RESPIRATORY DISEASE

Editor- Toft and Beckett finish their review of thyroid function
tests in hypothyroidism with the intriguing statement that residual
symptoms in treated patients might relate to the underlying chronic
inflammatory disorder rather than subtle abnormalities of thyroid hormone
status.(1) This struck a cord with us since we have noted a striking
excess of cases of treated hypothyroidism amongst a population of
idiopathic chronic cough(2) and in non-smokers with fixed airflow
obstruction(3) and have shown that idiopathic chronic cough is associated
with a bronchoalveolar lavage lymphocytosis.(2) We have suggested that
this may be due to homing of activated lymphocytes from the primary site
of autoimmune inflammation to embryologically related structures such as
the airways.(2-4)

The mechanism of airway inflammation and damage in autoimmune thyroid
disease may be analogous to that thought to be responsible for airway
complications of inflammatory bowel disease. The concept that inflammatory
bowel disease and autoimmune thyroid disease are associated with airway
disease and that the pathogenesis is similar and not related to thyroid
hormone status is supported by a recent study showing a 2-3 fold excess of
cough, sputum production and breathlessness, and a remarkably similar
profile of respiratory symptoms, amongst a cohort of patients with
inflammatory bowel disease and another with treated autoimmune thyroid
disease.4 Further evidence for a link between thyroid disease and
respiratory disease independent of thyroid hormone status has been
reported in a study showed a 2-3 fold increase in death from respiratory
disease in a large cohort of patients with normal thyroxine but suppressed
thyrotropin.(5)

These findings would be consistent with the view of thyroid disease
as a generalised, rather than organ-specific autoimmune disease. It is
tempting to speculate that other non-specific symptoms as well as
recognised complications of hypothyroidism such as ischaemic heart disease
are related to similar inflammatory mechanisms.

References

1. Toft AD,.Beckett GJ. Thyroid function tests and hypothyroidism.
BMJ 2003;326:295-6.

2. Birring S.S., Brightling, C. E., Symon, F. A., Barlow, S.,
Wardlaw, A. J., and Pavord ID. Lymphocytic bronchoalveolitis in idiopathic
chronic cough. Thorax 57, iii1. 2002.

3. Birring SS, Brightling CE, Bradding P, Entwisle JJ, Vara DD, Grigg
J et al. Clinical, radiologic, and induced sputum features of chronic
obstructive pulmonary disease in nonsmokers: a descriptive study.
Am.J.Respir.Crit Care Med. 2002;166:1078-83.

4. Birring S.S., Morgan A.J., Prudon B, McKeever T.M., Lewis S.A.,
Falconer Smith J.F., Robinson R.J., Britton J.R., and Pavord ID.
Respiratory symptoms in patients with treated hypothyroidism and
inflammatory bowel disease. Thorax in press. 2003.

5. Parle JV, Maisonneuve P, Sheppard MC, Boyle P, Franklyn JA.
Prediction of all-cause and cardiovascular mortality in elderly people
from one low serum thyrotropin result: a 10-year cohort study. Lancet
2001;358:861-5.

Competing interests:  
None declared

Competing interests: No competing interests

20 March 2003
Surinder S Birring
Specialist Registrar in Respiratory Medicine
Ronak B Patel and Ian D Pavord.
Institute for Lung Health, Department of Respiratory Medicine, Glenfield Hospital, Leicester, LE39QP