Inflammatory disorders of thyroid gland are a mixture of various
disorders characterized by variable clinical presentations, etiologies
and treatment modalities. These disorders cause the thyroid gland to be
diffusely enlarged, nodular. Functionally speaking these patients may
be euthyroid, hypothyroid or hyperthyroid. These patients may not
suffer from pain except in cases of post viral and suppurative
Inflammatory thyroiditis are often associated with certain characteristic triggering factors:
2. Viral infections
Classification of inflammatory thyroid disorders:
This takes into account the subjective history (painful or painless),
its temporal course (acute, subacute or chronic), histopathologic
features (hyperplastic, lymphocytic, granulomatous, or fibrous), and
the name of the physician who first described them (Graves, Hashimoto,
DeQuervain, and Riedel). These parameters cause a lot of confusion when
classifying this disorder.
A simple classification of inflammatory thyroiditis has been evolved. It divides the various disorders into four main groups:
2. Amiodarone induced
Autoimmune thyroid disease:
This is the commonest of inflammatory thyroid disorders. Disorders under this group include:
a. Hashimoto's thyroiditis (Chronic lymphocytic thyroiditis)
b. Subacute lymphocytic thyroiditis
c. Postpartum thyroiditis
d. Grave's disease
group of disorders is characterized by immune reaction against thyroid
autoantigens. There are three serologic markers for disorders belonging
to this group. They are:
1. Antibodies against thyroid globulin (the large protein on which T3 and T4 are synthesized and subsequently cleaved)
2. Thyroid microsomal antigen (also known as thyroid peroxidase)
3. Thyrotropin receptor
presence of thyroid antibodies facilitates lymphocytic infiltration of
the thyroid gland which is a feature of autoimmune thyroiditis. If
thyroid receptor stimulating antibody is present, it can cause
hypertrophy of the gland with minimal lymphocytic infiltration. This
picture is seen in Graves disease.
also can induce a thyrotropin receptor antibody which blocks normal
thyrotropin from activating it causes hypothyroidism without
Autoimmune thyroid disease may present
either with thyroiditis or as a hyperplastic disorder i.e. Graves
disease. When a clear precipitating factor could be associated with
this disorder then it could be used to name the subtype of the disorder
i.e. (Postpartum thyroiditis, interferon induced thyroiditis) etc.
Sometimes these various subtypes of autoimmune thyroiditis could be
seen in the same patient.
is the most common inflammatory disorder of thyroid gland. Patients
present typically with goitre, nodules, with hypothyroidism. High
titres of circulating thyroid antibodies is a feature of this disorder.
Histologically, the gland shows follicular degeneration with a
diffuse lymphocytic infiltration. There may also be associated
fibrosis. These features are identifiable in FNAC. If there is palpable
cervical node associated with Hashimotos thyroiditis then FNAC of
thyroid should be performed to rule out malignancy.
Diagram showing thyroid enlargement in Hashimoto's thyroiditis
Histology showing lymphocytic infiltration into the glandular tissueSubacute lymphocytic thyroiditis:
This disorder comprises of three subtypes. They are Postpartum
thyroiditis, silent thyroiditis and interferon induced thyroiditis. All
these three subtypes have positive microsomal antibodies.
thyroiditis: affects 5% of females. Women with positive thyroid
antibodies during the first trimester of pregnancy have roughly 50%
chance of developing postpartum thyroiditis. Hyperthyroidism usually
develops during the first three months following delivery. It is
usually mild and may last for a few months. The patient may then become
euthyroid and later hypothyroid. These patients commonly have a mild to
moderately enlarged thyroid gland. TSH levels may be raised.
Antithyroid drugs are not indicated in these patients on the other hand
steroids may have a role to play.
Silent thyroiditis has no clear
cut precipitating risk factors. Silent thyroiditis may precede or
succeed other types of autoimmune thyroiditis. The diagnosis is usually
one of exclusion.
Interferon a commonly used immunoactivating
agent in the treatment of viral hepatitis can cause thyroid
dysfunction. Pre existing auto immune thyroiditis is considered to be a
risk factor in the development of interferon induced thyroiditis. This
type of thyroiditis is generally mild and self limiting.Graves disease: is
an autoimmune disorder involving the thyroid gland. It also carries
with it the risk of developing other subtypes of autoimmune
thyroiditis. The classic presentation of Graves disease include:
4. Dermopathy (unusual)
Tests used to diagnose Graves disease:
Hyperthyroidism in Graves disease is caused by activating thyroid
stimulating antibody against the thyrotropin receptor. There is also an
increased incidence of thyroid carcinoma in these patients.
- Serum TSH estimation (elevated)
- Total or free T4 assessment
- Presence of microsomal antibodies
- Radioactive iodine uptake
the short term these patients can be managed with antithyroid
medications. Long lasting effects can be produced with ablation of
gland function by 131I administration, followed by life long supplements of thyroid hormones.
ablation of the gland is another option. Before embarking on it the
patient should be made euthyroid by use of antithyroid drugs. Oral
administration of Iodine should be discouraged in these patients unless
and until the patient has been started on antithyroid drugs.
Radioactive iodine uptake studies:
Amiodarone induced thyroiditis:
Amiodarone is a potent antiarrhythmic drug. This drug is structurally
related to thyroxine. It initially causes hyperthyroidism which is
unwelcome in cardiac patients. The types of thyroid dysfunction caused
by amiodarone is as follows:
|Toxic multinodular goitre
|Normal to high
|Homogenous / diffuse
Type I: This type behaves like toxic
multinodular goitre or graves disease with normal or high radioactive
iodine uptake. It responds well to antithyroid medications.
Type II: Behaves like chemical thyroiditis and is responsive to steroids.
Diagnostic tests to clinch the diagnosis include:
1. TSH estimation
2. Free T3 T4 estimation
3. Microsomal antibodies
4. Radio active iodine uptake scan
In most of the cases it is necessary to discontinue the drug.
Thyroidectomy may be considered in patients who need to continue taking
amiodarone because of their heart condition.Infectious thyroiditis:
Is commonly caused by viral infections. Post viral thyroiditis is also
known as De Quervain's disease, whereas bacterial thyroiditis tend to
suppurate. Suppurative thyroiditis is painful.
Also known as Riedel's thyroiditis. This is a very rare entity causing
fibrosis of thyroid gland and surrounding tissue. Etiology is unknown.
It is associated with retroperitoneal fibrosis, pseudo tumor of orbit
and sclerosing cholangitis. Majority of patients are women in the fifth
decade of life.
Diagnosis involves use of biopsy. In cases of
tracheal compression, excision of isthmus will suffice. Otherwise it is
a self limiting disease.
Medical therapy includes glucocorticoid administration. Tamoxifen could also be used.