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therefore, adequate biochemical testing is required for evaluation.
Diagnosis
Detailed description of the dynamic tests used is not appropriate to this text, but the basic principle is
assay of the relevant trophic hormones and cortisol levels, which will be low.
Treatment
The individual is treated to replace the deficiencies documented, usually with hydrocortisone 20 mg in the
morning and 10 mg in the afternoon (or cortisone acetate 25 mg + 12.5 mg) to simulate the normal
circadian rhythm. Thyroxine may or may not be required depending on the biochemical investigations.
Hypopituitarism is treatable and the patient should be able to perform normal activities as long as an
appropriate hormonal therapy is used consistently and properly. Once the appropriate regime has been
determined with appropriate laboratory back-up, the doses rarely need to be changed except for an
increase in the glucocorticoid dose (which is generally doubled) during inter-current illness. Even after
the proper regime has been stabilised, life long follow up by a specialist in endocrinology is required.
Operational indications
Florid hypopituitarism is clearly incompatible with aviation duties.
Aeromedical considerations
If the applicant has panhypopituitarism with multiple replacement therapy, medical certification will
normally not be possible. The possibility of not having replacement drugs taken consistently and properly
and the risk of intermittent illness away from specialised help have obvious implications.
Anterior pituitary hyperfunction
Most syndromes of hyperfunction are due to pituitary tumours. The particular syndrome presenting will
depend on which cell in the pituitary is involved. The tumours are mostly benign epithelial neoplasms that
result from mutation and subsequent expansion of single adenohypophyseal parenchymal cells. They
account for 10-15 per cent of intracranial neoplasms and 75 per cent of them secrete inappropriate
amounts of pituitary hormones. The presence of residual cells in the parasellar structures following
treatment may account for local recurrences, but metastatic spread and direct invasion of surrounding
structures is rare.
The majority of patients with pituitary adenomas present with signs and symptoms of hormone
hypersecretion, visual field defects and headaches, either alone or in combination.
ICAO Preliminary Unedited Version — March 2010 III-4-6
The diagnosis is usually clear from the history and examination, but should be confirmed by pituitary
imaging (CT-scanning and MRI) and specific hormone assays.
SPECIFIC CLINICAL SYNDROMES
Over-production of growth hormone (GH)
Aetiology and Pathogenesis
Over-secretion of GH by an eosinophilic tumour of the pituitary gland will produce acromegaly in the
adult.
Clinical features
The diagnosis is made from the classic clinical features:
a) coarse facial features
b) jaw growth and malocclusion
c) hypertrichosis
d) tiredness, weakness and somnolence
e) carpal tunnel syndrome
f) possible hypertension with or without cardiomegaly
g) impaired glucose tolerance
Investigation
The diagnosis is confirmed by increased basal growth hormone levels on two or more occasions (>5
mU/L or 2.5 ng/mL), particularly with a raised concentration of insulin-like growth factor I. Borderline
cases may require a glucose tolerance test, which in the normal individual would suppress growth
hormone to levels below 2 mU/L.
Radiological investigation
In 90 per cent of cases, a lateral skull X-ray shows enlargement of the pituitary fossa with or without
erosion of the clinoid processes.
Treatment
Transphenoidal surgery reduces circulating growth hormone in 60 per cent of patients, but normal
pulsatile growth hormone may not be restored. Radiotherapy alone produces an annual fall in growth
hormone of approximately 20 per cent, improves headaches in over 75 per cent of patients, and reduces
the risk of further visual loss due to tumour expansion. In many centres radiotherapy produces similar
results to surgery but it may take up to four years for growth hormone levels to fall to <2mU/L in a
glucose tolerance test. In 50 per cent of patients, growth hormone levels remain elevated ten years post
surgery, and in the long term hypopituitarism may develop.
Bromocriptine may reduce growth hormone in about 75 per cent of mild cases but rarely produces levels
below 10 mU/L. However, it may produce nausea, vomiting and postural hypotension. Somatostatin
analogues (e.g. octreotide) have replaced dopamine agonists as the first line medical treatment for
somatotroph adenomas. They are given by injection twice or thrice daily. They reduce circulating growth
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Manual of Civil Aviation Medicine 1(124)
