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goitre or a single autonomously functioning solitary nodule (toxic adenoma).
1 Grave’s disease: diffuse toxic goitre, named after Robert James Graves, Irish physician (1796-1853)
2 Basedow’s disease: the same, named after Karl Adolf von Basedow, German physician (1799-1854)
ICAO Preliminary Unedited Version — March 2010 III-4-2
Grave’s disease results from the stimulation of thyrotrophin receptors on thyroid follicular cells by
circulating TSH-receptor antibodies of the IgG class. Genetic factors may play a role with the association
of various HLA-DR antigens (Human Leucocyte Antigens), especially HLA-DR3, although no specific
gene has been shown to confer a strong susceptibility to the condition.
Clinical features
Classically patients develop heat intolerance, sweating, and weight loss in spite of increased appetite.
They may be anxious and irritable and are often depressed. In women menstrual upset is common.
Palpitations are frequent symptoms, and the elderly may develop atrial fibrillation. Goitre (struma) may
be present and there may be a thrill or bruit over the gland. The clinical features are those of increased
sensitivity to circulating catecholamines. There may be elevation of levator palpebrae superioris, giving a
startled appearance, and personality changes may be marked.
Mild ocular involvement with proptosis is an integral part of the clinical syndrome of Grave’s disease.
However, severe ophthalmopathy occurs in 25-50 per cent of cases with marked proptosis,
ophthalmoplegia, chemosis and increasing retro-orbital pressure, which can lead to papilloedema or optic
atrophy with loss of vision (malignant exophthalmos). These severe eye signs usually accompany the
general picture of hyperthyroidism, but may occur after the patient has been treated and is euthyroid.
Investigation of thyrotoxicosis
Laboratory analysis of TSH, T3 and T4 by radioimmuno-assay has simplified the biochemical diagnosis.
TSH is low or undetectable, and T3 and T4 are elevated. T3 may be raised before T4 and this makes early
diagnosis possible.
If there is a nodular goitre, imaging techniques may be useful with scans using 99mTc labelled
pertechnetate.
Management of thyrotoxicosis
There are three forms of treatment for hyperthyroidism: medical, radioactive iodine, and surgical.
a) Medical management. The major anti-thyroid drugs are thiourea compounds. Carbimazole is
used widely in the United Kingdom and propylthiouracil and methimazole in the United States.
Treatment is usually continued for 12-18 months; the relapse rate is high.
Beta-blockers (e.g. propranolol) are useful for the relief of symptoms in the first 1-2 months until
the definitive treatment renders the patient euthyroid.
b) Surgical management. This kind of surgery is only carried out in specialist centres; the
indications vary, and patient preference may influence decisions. Potential problems include
recurrent laryngeal nerve trauma, damage to the parathyroid glands, and late hypothyroidism.
c) Radioactive iodine. In many centres this is now the treatment of choice for toxic multinodular
goitres; it is increasingly being used for Grave’s disease and the single hot nodule. There are
numerous regimes in use and all accept that the patient will become hypothyroid and thus will
require lifelong thyroxine.
ICAO Preliminary Unedited Version — March 2010 III-4-3
Operational implications
Frank thyrotoxicosis is obviously incompatible with aviation duties until stable euthyroidism has been
established and a satisfactory report from an endocrinologist is received.
Aeromedical considerations
Applicants with hyperthyroidism may be considered for medical assessment in any class when they have
been euthyroid for at least two months. The continued use of anti-thyroid drugs is usually well tolerated;
side effects are rare and should not preclude safety-sensitive duties. A condition of the medical certificate
should be life-long follow-up by an endocrinologist to ensure no recurrence of the hyperthyroidism and
no insidious onset of late hypothyroidism.
Hypothyroidism
Isolated hypothyroidism beginning in adult life is almost always due to autoimmune thyroid disease or
previously treated hyperthyroidism. It is a common condition, affecting one per cent of the general
population and there are data to show that four per cent of those over 60 years of age are on long-term
treatment with thyroxine. Hypothyrodism may be caused more rarely by failure of hypothalamic
production of TRH or pituitary production of TSH.
Hypothyroidism is more common in females with a 5-10 fold lower prevalence in males.
Clinical features
The onset is gradual and often the diagnosis is not recognised for some time. The signs and symptoms
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Manual of Civil Aviation Medicine 1(122)
