THYROID GLAND
Dr.Mohanned Alshalah
LEC 2
Hyperthyroidism
The term thyrotoxicosis is retained because hyperthyroidism, i.e. symptoms due
to a raised level of circulating thyroid hormones, is not responsible for all
manifestations of the disease.
Clinical types are:
•diffuse toxic goitre (Graves’ disease)
•toxic nodular goitre;
•toxic nodule;
•hyperthyroidism due to rarer causes.
Thyrotoxicosis is eight times more common in women than in men.
Clinical features
The symptoms are:
•tiredness;
•emotional lability;
•heat intolerance;
•weight loss;
•excessive appetite;
•palpitations.
The signs of thyrotoxicosis are:
•tachycardia;
•hot, moist palms;
•exophthalmos;
•lid lag/retraction;
•agitation;
•thyroid goitre and bruit.
The most significant symptoms are loss of weight despite a good appetite, a
recent preference for cold, and palpitations.
The most significant signs are the excitability of the patient, the presence of a
goitre, exophthalmos and tachycardia or cardiac arrhythmia.
Diffuse toxic goitre (Graves’ disease):
A diffuse vascular goitre, a thrill and a bruit may be present. It usually occurs in
younger women and is frequently associated with eye signs. 50% of patients have
a family history of autoimmune endocrine diseases.
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THYROID GLAND
Dr.Mohanned Alshalah
LEC 2
The thyroid tissue is hypertrophy and hyperplasia due to abnormal thyroidstimulating antibodies (TSH-RAbs) that bind to TSH receptor sites and produce a
disproportionate and prolonged effect. The onset is abrupt, but remissions and
exacerbations are not infrequent.
Hyperthyroidism is usually more severe than in secondary thyrotoxicosis but
cardiac failure is rare. Manifestations of thyrotoxicosis not due to
hyperthyroidism e.g. orbital proptosis, ophthalmoplegia and pretibial
myxoedema, may occur in primary thyrotoxicosis.
Toxic nodular goitre
A simple nodular goitre is present for a long time before the hyperthyroidism,
usually in the middle-aged or elderly. The syndrome is that of secondary
thyrotoxicosis. In secondary thyrotoxicosis the goitre is nodular.
The onset is insidious and may present with cardiac failure or atrial fibrillation.
It is characteristic that the hyperthyroidism is not severe. Eye signs other than lid
lag and lid spasm (due to hyperthyroidism) are very rare.
Toxic nodule
A toxic nodule is a solitary overactive nodule, which may be part of a generalised
nodularity or a true toxic adenoma. It is autonomous and its hypertrophy and
hyperplasia are not due to TSH-RAb.
TSH secretion is suppressed by the high level of circulating thyroid hormones and
the normal thyroid tissue surrounding the nodule is itself suppressed and inactive.
Diagnosis of thyrotoxicosis
Most cases are readily diagnosed clinically.
Hyperthyroidism is confirmed biochemically by raised level of circulating thyroid
hormones and decrease TSH level. A TRH test is rarely indicated.
T3 thyrotoxicosis is diagnosed by estimating the free T3.
It should be suspected if the clinical picture is suggestive but routine tests of
thyroid function reveal a normal T4 but suppressed TSH.
A thyroid scan is required to diagnose an autonomous toxic nodule and
differentiate it from a dominant swelling in a toxic multinodular goitre.
Principles of treatment of thyrotoxicosis
Non-specific measures are rest and sedation.
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THYROID GLAND
Dr.Mohanned Alshalah
LEC 2
Specific measures:
Anti-thyroid drugs
Those in common use are carbimazole and propylthiouracil.
β- Adrenergic blockers such as propranolol and nadolol are used to block the
cardiovascular effects of the elevated T4.
Iodides, which may reduce the vascularity of the thyroid, should be used only as
immediate preoperative preparation in the 10 days before surgery.
Anti-thyroid drugs are used to restore the patient to a euthyroid state and to
maintain this for a prolonged period in the hope that a permanent remission will
occur, i.e. that the production of TSH-RAbs will diminish or cease.
Anti-thyroid drugs cannot cure a toxic nodule. The overactive thyroid tissue is
autonomous and recurrence of the hyperthyroidism is certain when the drug is
discontinued.
Advantages:
No surgery and no use of radioactive materials.
Disadvantages:
•Treatment is prolonged and the failure rate after a course of 1.5—2 years is at
least 50 per cent.
It is impossible to predict which patient is likely to go into a remission.
•Some goitres enlarge and become very vascular during treatment —even if
thyroxine is given at the same time. This is probably due to TsAb stimulation
during the prolonged course of treatment and not a direct effect of the drug.
•Very rarely, there is a dangerous drug reaction, e.g. agranulocytosis or aplastic
anaemia.
Surgery
In diffuse toxic goitre and toxic nodular goitre with overactive internodular tissue,
surgery cures by reducing the mass of overactive tissue. Cure is probable if the
thyroid tissue can be reduced below a critical mass but there is a risk of both
permanent thyroid failure and recurrence of toxicity following subtotal resection.
In the autonomous toxic nodule, and in toxic nodular goitre with overactive
autonomous toxic nodules, surgery cures by removing all of the overactive
thyroid tissue; this allows the suppressed normal tissue to function again.
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THYROID GLAND
Dr.Mohanned Alshalah
LEC 2
• Advantages: The goitre is removed, the cure is rapid and the cure rate is high if
surgery has been adequate.
• Disadvantages:
Recurrence of thyrotoxicosis occurs in approximately 5% of cases if less than total
thyroidectomy is carried out.
There is a risk of permanent hypoparathyroidism and nerve injury.
Young women tend to have a worse cosmetic result from the scar.
Postoperative thyroid insufficiency occurs in 20–45% of cases.
Long-term follow-up is necessary as the few patients who develop recurrence
may do so at any time in the future.
In addition, although it is usually apparent within 1 or 2 years, thyroid failure may
also be a late development.
Parathyroid insufficiency should be permanent in less than 0.5%.
Radioiodine
Radioiodine destroys thyroid cells and, as in thyroidectomy, reduces the mass of
functioning thyroid tissue to below a critical level.
Advantages:
No surgery and no prolonged drug therapy.
Disadvantages:
•Isotope facilities must be available.
•There is a high and progressive incidence of thyroid insufficiency which may
reach 75—80 per cent after 10 years.
•Indefinite follow-up is essential.
Choice of therapy;
Patients must be considered individually.
In advising treatment, compliance, influenced by social and intellectual factors, is
important; many patients cannot be trusted to take drugs regularly if they feel
well, and indefinite follow-up, which is essential after radioiodine or subtotal
thyroidectomy, is a burden for all.
Diffuse toxic goitre
In patients over 45 years, radioiodine is appropriate.
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THYROID GLAND
Dr.Mohanned Alshalah
LEC 2
In those under 45 years, surgery for the large goitre and anti-thyroid drugs or
radioiodine for the small goitre is recommended.
Toxic nodular goitre
Large goitres should be treated surgically because they do not respond as well as
rapidly to radioiodine or anti-thyroid drugs as a diffuse toxic goitre.
Toxic nodule
Surgery or radioiodine treatment is appropriate.
Resection is easy, certain and without morbidity.
Radioiodine is a good alternative for those over the age of 45 years because the
suppressed thyroid tissue does not take up iodine and there is thus no risk of
delayed thyroid insufficiency.
Recurrent thyrotoxicosis after surgery
Radioiodine is the treatment of choice, but antithyroid drugs may be used in
young women intending to have children.
Further surgery has little place.
Problems in treatment of thyrotoxicosis in Pregnancy ??
Surgery for thyrotoxicosis
Preoperative preparation
Traditional preparation aims to make the patient biochemically euthyroid at
operation. The thyroid state is determined by clinical assessment, i.e. by
improvement in previous symptoms and by objective signs such as weight gain
and lowering of the pulse rate, and by serial estimations of the thyroid profile.
Carbimazole 30–40 mg/ day is the drug of choice for preparation.
When euthyroid (after 8–12 weeks), the dose may be reduced to 5 mg 8-hourly or
a ‘block and replace’ regime used .
Iodides are not used alone because if the patient needs preoperative treatment a
more effective drug should be given.
An alternative method of preparation is to abolish the clinical manifestations of
the toxic state using β-blocking drugs. β- Blockers act on the target organs and not
on the gland itself. Propranolol inhibits the peripheral conversion of T4 to T3. This
result in very rapid control and operation may be arranged within 1 week.
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THYROID GLAND
Dr.Mohanned Alshalah
LEC 2
β -Blockers do not interfere with synthesis of thyroid hormones, and hormone
levels remain high during treatment and for some days after thyroidectomy. It is
therefore important to continue to give the drug for 7 days postoperatively.
Iodine may be given with carbimazole or β-blocker for the 10 days before
operation. Iodide alone produces a transient remission and may reduce vasularity,
thereby marginally improving safety.
Propranolol or nadolol controls symptoms very rapidly and has additional value in
combination with carbimazole in the immediate treatment of patients with very
severe hyperthyroidism.
Preoperative investigations to be carried out and recorded are:
• Thyroid function tests.
• Laryngoscopy.
• Thyroid antibodies.
• Serum calcium estimation.
• An isotope scan before preoperative preparation in toxic nodular goitre if total
thyroidectomy is not planned.
Postoperative complications
Haemorrhage
Respiratory obstruction
Recurrent laryngeal nerve paralysis and voice change may be unilateral or
bilateral, transient or permanent.
Thyroid insufficiency (20–45%)
Parathyroid insufficiency: The incidence of permanent hypoparathyroidism should
be less than 1% and most cases present dramatically 2–5 days after operation.
Thyrotoxic crisis (storm): It occurs if a thyrotoxic patient has been inadequately
prepared for thyroidectomy.
Wound infection
Hypertrophic or keloid scar
Stitch granuloma
Recurrent thyrotoxicosis: (5%) after subtotal thyroidectomy for Graves’ disease
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