Thyroid disease is defined as a condition of malfunction of thyroid.
Hyperthyroidism is a condition in which the thyroid gland is over active
and produces too much thyroid hormones. Hypothyroidism is a condition
in which the thyroid gland is under active and produces very little
thyroid hormones. Thyroid cancer is defined as condition in which the
cells in the thyroid gland have become cancerous.
Silent thyroiditis
Silent thyroiditis is the inflammation of the thyroid gland. Patients
with silent thyroiditis are experience back and forth between
hypothyroidism and hyperthyroidism. The disease classically present with
a triphasic course: a brief period of thyrotoxicosis due to release of
preformed thyroid hormone that lasts for 1 to 3 months, followed by a
more prolonged hypothyroid phase lasting up to 6 months, and eventual
return to a euthyroid state. However, the types and degree of thyroid
dysfunction are variable in these disorders, and individual patients may
present with mild or more severe cases of thyrotoxicosis alone,
hypothyroidism alone, or both types of thyroid dysfunction(a).
B. Causes and Risk factors
B.1. Causes
Although the cause of silent thyroiditis is known. The autoimmune
thyroiditis processus progressively and slowly tends to the
necrosis/apoptosis of thyroid cells and their functional impairment.
Other forms of autoimmune thyroiditis, postpartum thyroiditis and silent
thyroiditis(11). There is a suggestion that silent thyroiditis is an
autoimmune disease characterized by lymphocytic infiltration of the
thyroid and by transient hyperthyroidism, followed occasionally by
transient hypothyroidism and eventual recovery(12).
Other indicated that clinically important autoimmune thyroid disease
might thus be present both in individuals with normal and with raised
thyrotropin concentrations. Rises in thyrotropin concentration might
also occur for several reasons other than autoimmune thyroiditis(13).
B.2. Risk factors
1. Gentic and environment factors
Genetic and/or environmental factors are important in the development of
this familial type of silent thyroiditis, according to the study by the
Gifu Red Cross Hospital(14). Other study indicated that antecedent
infection or exposure to antigen may cause the development of silent
thyroiditis(15).
2. Adrenalectomy
There is a report of a case of silent thyroiditis after unilateral
adrenalectomy for treatment of Cushing’s syndrome as the left
adrenocortical adenoma was resected, according to the Gifu University
School of Medicine(16).
3. Lithium therapy
While hypothyroidism secondary to treatments by lithium are well known,
cases of hyperthyroidism are less common. A 48 years old patient under
lithium carbonate from about 10 years ago presents hyperthyroidism
without any auto-immunity biological markers, associated with a very low
thyroid tracer uptake on scintigraphy(17).
4. Alpha-interferon therapy
There is a report of a a 30-year-old woman with chronic active hepatitis
C develops silent thyroiditis developed during alpha-interferon
therapy(18). Other study report the development of a episode of silent
thyroiditis in a patient with chronic thyroiditis and papillary
adenocarcinoma following alpha interferon treatment for hepatitis C(19).
5. Thyroid-stimulation-blocking antibodies (TSBAb)
There is a report of a 24-year-old man showed thyrotoxic symptoms with
hypokalemic periodic paralysis. Serum thyroid hormone levels were high
and thyrotropin (TSH) was undetectable. 123I-thyroidal uptake was
suppressed. TSH-binding inhibitor immunoglobulin (TBII) was
positive(20).
6. Infections
Viral infection such as rubella could cause the development of silent
thyroiditis. There is a report of A 40-year-old housewife was referred
to our hospital for evaluation of a thyrotoxic state. A month after
rubella infection, she developed heat intolerance(21).
7. Gender
If you are women, you are associated to increased risk of silent thyroiditis
8. Low level of selenium
Se levels were significantly decreased in cases of sub-acute and silent thyroiditis. according to WOMED(22).
9. Postpartum period
Silent or painless thyroiditis is a frequent cause of transient
hyperthyroidism, which is characterized by recent onset of symptoms in a
patient with a normal to modestly enlarged and firm thyroid gland. No
pathogenetic factors are known, but the disease may conceivably have an
autoimmune basis, particularly in the postpartum patient(22a).
10. Autoimmune type 1 diabetes mellitus
Patients with autoimmune type 1 diabetes mellitus have often, besides
immune diabetes markers, also other organ-specific antibodies,
particularly thyroid autoantibodies (antithyreoglobulin antibodies – ATG
and/or thyroid peroxidase antibodies – TPO)(22b).
11. Thyroid peroxidase autoantibodies
Thyroid peroxidase (TPO) is a key enzyme in the formation of thyroid
hormones and a major autoantigen in autoimmune thyroid diseases. Titers
of TPO antibodies also correlate with the degree of lymphocytic
infiltration in euthyroid subjects, and they are frequently present in
euthyroid subjects (prevalence 12-26%)(22c).
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Sources
(13) http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2801%2905358-2/fulltext#bib5
(14) http://www.ncbi.nlm.nih.gov/pubmed/16284442.
(15) http://www.ncbi.nlm.nih.gov/pubmed/1752238
(16) http://www.ncbi.nlm.nih.gov/pubmed/8484389
(17) http://www.ncbi.nlm.nih.gov/pubmed/17166635
(18) http://www.ncbi.nlm.nih.gov/pubmed/8128980
(19) http://www.ncbi.nlm.nih.gov/pubmed/7920883
(20) http://www.ncbi.nlm.nih.gov/pubmed/1983199
(21) http://www.ncbi.nlm.nih.gov/pubmed/2384053
(22) http://www.ncbi.nlm.nih.gov/pubmed/18221503
(22a) http://www.ncbi.nlm.nih.gov/pubmed/21278944
(22b) http://www.ncbi.nlm.nih.gov/pubmed/23599721
(23c) http://www.ncbi.nlm.nih.gov/pubmed/15826919
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