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Causes
1°:
From disease of thyroid (commoner)
Congenital: agenesis, ectopic.
Defects in hormone synthesis:
Iodine
deficiency.
Dyshormogenesis.
q
Rare.
q
Familial
form is associated with sensorineural deafness (Pendred’s
syndrome).
Antithyroid
drugs.
Other drugs (lithium,
amiodarone, IFN).
Autoimmune:
Hashimoto’s thyroiditis.
Infective:
Post-subacute thyroiditis (de Quervain’s).
Post thyroidectomy.
Radioactive iodine therapy.
2°:
to hypothalamic-pituitary disease (i.e. ¯
TSH drive) à
Hypopituitarism
v
Hashimoto’s thyroiditis:
q
Autoimmune
& commonest cause.
q
Pathology:
§
Atrophic changes with
regeneration à goiter formation.
§
Lymphoid infiltration of gland.
q
Auto-Abs: 1) Anti-microsomal (anti-peroxidase ) Abs titer.
2)
Anti-thyroglobulin Abs
titer.
q
Associated
with other organ-specific autoimmune diseases.
q
Risk of lymphoma.
v
Postpartum thyroiditis:
q
Silent
painless thyroiditis.
q
Transient,
follows pregnancy.
q
Results
from modifications to immune system necessary in pregnancy.
q
Self-limiting
(75%).
Clinical
Features
Pericardial effusion
|
↓
Appetite
|
Thick
skin
|
|
Bradycardia
|
Weight
gain (adults)
|
Dry
hair
|
|
↓
Voltage in ECG
|
Constipation
|
Cold
intolerance
|
Mental slowness
|
Deep
voice
|
Myxedema
|
Lethargy
|
↓
Reflexes
|
↓
Amenorrhea
|
N.B. Myxedema:
accumulation of mucopolysaccharide in subcutaneous tissues.
Investigations
1.
1°
hypothyroidism:
TSH =
T4, T3 =
¯
2.
2°
hypothyroidism:
TSH = N / ¯
T4, T3 =
¯
3.
Hypercholestrolemia.
·
Thyroid
& other organ-specific Abs may be present.
Treatment
1°
hypothyroidism:
·
Replacement
therapy with thyroxine is given for life.
·
Adequacy
of replacement should be assessed clinically & by TFTs (TSH
& possibly T4) after at least 6 weeks on a steady
dose.
·
Aim:
restore TSH to well within normal range.
2°
hypothyroidism:
Thyroxine.
v
Myxedema
coma:
·
Very
rare severe hypothyroidism, esp elderly.
·
Confusion,
coma, hypothermia, severe cardiac failure, hypoventilation,
hypoglycemia, hyponatremia.
written
by:
Khalid Bin Yaroof. FMHS, UAE University.
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