Page 437 - Medicine and Surgery

P1: FAW
BLUK007-11 BLUK007-Kendall May 25, 2005 8:5 Char Count= 0

Chapter 11: Thyroid axis 433

Respiratory system: Respiration may be slow and shal- Aetiology

low. Respiratory failure occurs in myxoedema coma. Patients have detectable anti-microsomal antibody and
Gastrointestinal system: Reduced peristalsis, leading antithyroglobulin antibodies in most cases. Other au-

to chronic constipation. Ileus may occur. toantibodies include anti-thyroid cell cytosol and anti-
Genitourinary system: Impaired ability to excrete wa- microsomes associated with HLA-DR5 and other au-

terpredisposes to water overload. Women may have toimmune diseases such as vitiligo and SLE.
menstrual irregularities, particularly heavy periods.
Haematological: Anaemia (normally normochromic/ Clinical features

normocytic). The patient, typically a postmenopausal female, presents
Other signs include a cool rough dry skin, hair loss, with a diffuse goitre. Although most patients are euthy-

puffy face and hands, a hoarse husky voice and slowed roid, thyrotoxicosis can occur and if presentation is late,
reflexes. The skin may be yellowish (due to reduced hypothyroidism may be present. On examination, the
conversion of carotene to vitamin A). thyroid is firm and symmetrically enlarged with a bosse-
lated surface.
Complications
Pericardial and pleural effusions. Carpal tunnel syn- Macroscopy/microscopy
drome. Deafness due to fluid in the middle ear. The thyroid is diffusely enlarged and has a fleshy white
cut surface due to lymphocytic infiltration, which is seen
Investigations on microscopy around the destroyed follicles.
Hypothyroidism is confirmed by a low T 3 and T 4 (ex-

cept in end organ resistance) with a raised TSH in Investigations
primary hypothyroidism. Thyroid autoantibodies are High titres of circulating antithyroid antibodies, associ-
present in patients with autoimmune disease. ated with a goitre on examination.
Other investigations are aimed at diagnosing the un-

derlying cause and are indicated according to the his- Management
tory and clinical suspicion. Thyroxine may cause regression of small goitres. Large
goitres require subtotal thyroidectomy if causing com-
Management pression of local structures such as the oesophagus or
Thyroxine replacement starting with a low dose is re- trachea. Surgical complications include damage to the
quired for life. Treatment of elderly patients should be recurrent laryngeal nerves or parathyroids. Post-surgery
undertaken with care, as any subclinical ischaemic heart or following significant thyroid destruction patients be-
disease may be unmasked. Thyroxine dosing is titrated come hypothyroid requiring treatment with thyroxine
according to thyroid function tests. for life.

Hashimoto’s disease (autoimmune Myxoedema coma
thyroiditis)
Definition
Definition This is the end-stage of untreated hypothyroidism, lead-
Organ-specific autoimmune disease causing thyroiditis ing to progressive weakness, hypothermia, respiratory
and later hypothyroidism. failure, shock and death.

Age Incidence/prevalence
Peak in middle age. Rare

Sex Age
F > M (10:1) Mainly in elderly.