Hypothyrodism
This may occur in severely
anemic and/or iron overload patients. Usually appearing in the second decade of
life. The condition is uncommon in optimally treated patients (De Sanctis,
1998).
Thyroid dysfunction has been
reported in 18-60℅ of thalassemic patients, but severity is variable in
different series. Some studies reported a high prevalence reaching 17-18%,
others reported a low incidence of 0-9% (Pantelakis, 1994).
Signs and symptoms:
Pre-clinical hypothyroidism
is asymptomatic. In mild and overt hypothyroidism, symptoms such as growth
retardation, decreased activity, above normal weight, constipation and reduced
school performance, cardiac failure and pericardial effusion may be
encountered. The incidence of hypothyroidism is slightly higher in females.
Typically the thyroid gland is not palpable, thyroid antibodies are negative
and thyroid ultrasonography show an irregular echo pattern with thickening of
the capsule (De Sanctis, 1998).
Three types of thyroid dysfunction have
been recognized: pre-clinical – the classical symptoms of hypothyroidism are
absent; the serum FT4 is normal; TSH marginally increased and TSH response to
TRH is increased; mild hypothyroidism - growth retardation, tiredness and dry
skin may be present, serum FT4 is marginally low whilst TSH is elevated and TSH
response to TRH is exaggerated. In severe hypothyroidism - short stature,
decreased activity, dry skin, cardiac failure and pericardial effusion may be
present. The serum FT4 is low, TSH elevated and TSH response to TRH is
exaggerated. Treatment depends on the severity of the organ failure (De
Sanctis, 2008).
Annual investigations of
thyroid function is recommended, beginning at the age of 12 years. Free T4 and
TSH are the key investigations. The majority of patients have primary thyroid
dysfunction. Secondary hypothyroidism caused by iron-mediated damage of the
pituitary gland occurs very rarely (De Sanctis, 1998).
Treatment:
For severely affected patients gradual
replacement with L-thyroxine is recommended. In mild hypothyroidism the
decision to treat depends on each individual case. Preclinical hypothyroidism
requires only careful follow-up. In these cases, it was observed that a good
compliance to chelation therapy in iron overloaded patients may improve the
thyroid function. In 52% of thalassemic patients with preclinical
hypothyroidism the thyroid function was restored to normal following intensive
subcutaneous chelation therapy (De Sanctis, 2008).
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