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Hypothyroidism is defined as a deficiency in thyroid hormone
secretion and action that produces a variety of clinical signs and
symptoms of Hypometabolism.
Overt Hypothyroidism is defined as an elevated serum TSH
concentration (usually above 10 mIU/L) and reduced free
Thyroxine concentration (fT4)
2. Subclinical Hypothyroidism is defined as serum TSH above the
upper reference limit in combination with a normal free Thyroxine
According to a projection from various studies on Thyroid disease,
it has been estimated that about 42 million people in India suffer
from Thyroid diseases. The prevalence of Hypothyroidism was
3.9%. The prevalence of subclinical Hypothyroidism was 9.4%. In
women, the prevalence was higher, at 11.4%, when compared
with men, in whom the prevalence was 6.2%. The prevalence of
subclinical Hypothyroidism increased with age. About 53% of
subjects with subclinical hypothyroidism were positive for antiTPO antibodies.
these manifestations are largely independent of the
underlying disorder but are a function of the degree of
CAUSES OF HYPOTHYROIDISM
Hashimoto’s Thyroiditis is an autoimmune disease in which the thyroid gland is
attacked by a variety of cell and antibody-mediated immune processes, causing
primary Hypothyroidism. The resulting inflammation from Hashimoto’s disease,
also known as Chronic Lymphocytic Thyroiditis, often leads to an underactive
Thyroid gland (Hypothyroidism).
The diagnosis of Hashimoto’s Thyroiditis is supported by recognition of
autoantibodies against TPO or Thyroglobulin. 90% of patients with Hashimoto’s
Thyroiditis have anti-TPO antibodies and anti-Thyroglobulin antibodies, making
these antibodies excellent markers for Hashimoto’s Thyroiditis. Anti-TPO antibody
positivity is more common at the time of diagnosis than anti-Thyroglobulin
Hypothyroidism in Pregnancy
Convincing data suggest that pregnant women who are positive for Thyroid
autoantibodies (especially anti-TPO antibodies) leads to higher frequency of miscarriage
(13.8%) than is seen in pregnant women who lack anti-TPO antibodies (2.4%), and that T4
treatment of the anti-TPO antibody positive group reduces the risk of miscarriage to
Over Hypothyroidism (OH) in pregnancy is defined as an elevated TSH (>2.5 mIU/L)
in conjunction with a decreased FT4 concentration. Women with TSH levels of 10.0 mIU/L
or above, irrespective of their FT4 levels, are also considered to have OH.
Sub-clinical Hypothyroidism (SCH) in pregnancy is defined as a serum TSH between 2.5
and 10 mIU/L with a normal FT4 concentration.
Isolated Hypothyroxinemia (IH) is defined as a normal maternal TSH concentration
in conjunction with FT4 concentrations in the lower 5th or 10th percentile of the
10%-20% of all pregnant women in the first trimester of pregnancy are Thyroid
Peroxidase (TPO) or Thyroglobulin (Tg) antibody positive and Euthyroid
16% of the women who are Euthyroid and positive for TPO or Tg antibody in the
first trimester will develop a TSH that exceeds 4.0 mIU/L by the third trimester,
and 33%-50% of women who are positive for TPO or Tg antibody in the first
trimester will develop postpartum Thyroiditis
2%–3% of apparently healthy, non-pregnant women of childbearing age have an
elevated serum TSH. Among these healthy non-pregnant women of childbearing
age it is estimated that 0.3%-0.5% of them would, after having Thyroid function
tests, be classified as having OH, while 2%–2.5% of them would be classified as