Hyperthyroidism, also known as thyrotoxicosis, results from elevated thyroid hormones in the blood and causes hypermetabolism. Graves' disease is the most common cause, an autoimmune disorder where thyroid receptor antibodies stimulate excess thyroid hormone production. Women are more frequently affected than men. Laboratory tests show suppressed TSH and increased thyroid hormone levels. Graves' disease in pregnancy can cause fetal and neonatal hyperthyroidism or hypothyroidism if not properly managed.

1. HYPERTHYROIDISM

2. INTRODUCTION
 Hyperthyroidism, also known as Thyrotoxicosis, is the clinical
syndrome that results from elevated concentrations of free thyroid
hormone in the plasma, associated with clinical evidence of
hypermetabolism.

3. CAUSES

4. GRAVE’S DISEASE (GD)
 GD is overall the most common cause of Hyperthyroidism. GD is
caused by a generalized over activity of the entire thyroid gland
(Hyperthyroidism).
 GD is an autoimmune disorder in which Thyroid Receptor
Antibodies (TRAbs) stimulate the TSH receptor, increasing thyroid
hormone production.

5. Prevalance
 Women are more frequently affected by Grave’s Disease than men
by a 5:1 ratio. TRAbs are present in 70-100% of Grave’s Disease (85-
100% for activating antibodies and 75-96% for blocking antibodies).
 The prevalence of hyperthyroidism has been studied in several
studies in India.
 In an epidemiological study from Cochin, Subclinical and Overt
Hyperthyroidism were present in 1.6% and 1.3% of subjects
participating in a community survey.
 In a hospital-based study of women from Pondicherry, Subclinical
and Overt Hyperthyroidism were present in 0.6% and 1.2% of
subjects.

6. Pathogenesis
 The Hyperthyroidism of Grave’s Disease is caused by Thyroid
stimulating immunoglobulin that are synthesised in the thyroid
gland as well as in bone marrow and lymphnodes. A combination of
environmental and genetic factors, including polymorphism in HLA-
DR, CTLA-4, CD25, PTPN22 & TSH-R contribute to Grave’s Disease
susceptibility. Cytokines appear to play a major role in thyroid-
associated opthalmopathy.

7. Clinical Manifestations

8. Laboratory Evaluations
 In Grave’s Disease, the TSH level is suppressed & total and unbound
thyroid hormone levels are increased. In 2-5 % of patients, only T3
is increased (T3 toxicosis).
 Measurement of Thyroid receptor antibodies is the most reliable
diagnostic method if the diagnosis is unclear clinically.

9. A SCHEME FOR EVALUATING SUSPECTED
HYPERTHYROIDISM

11. HYPERTHYROIDISM IN PREGNANCY
 Graves’ disease is the most common cause of autoimmune
hyperthyroidism in pregnancy, occurring in 0.1%–1% (0.4% clinical and
0.6% subclinical) of all pregnancies. More frequent than Graves’
disease as the cause of thyrotoxicosis is the syndrome of gestational
hyperthyroidism defined as ‘‘transient hyperthyroidism, limited to the
first half of pregnancy characterized by elevated FT4 and suppressed
or undetectable serum TSH, in the absence of serum markers of
thyroid autoimmunity’’ . It is diagnosed in about 1%–3% of
pregnancies, depending on the geographic area and is secondary to
elevated hCG levels. Determination of TSH receptor antibody (TRAb)
is indicated for differentiating gestational hyperthyroidism from
Grave’s hyperthyroidism in pregnancy.

12. Fetal risks for women with active
Graves’ hyperthyroidism are
 1) fetal hyperthyroidism
 2) neonatal hyperthyroidism
 3) fetal hypothyroidism
 4) neonatal hypothyroidism
 5) central hypothyroidism

13. Recommendation
 If the patient has a past or present history of Graves’ disease, a
maternal serum determination of TRAb should be obtained at 20–24
weeks gestation for determining the risk of Neonatal Thyrotoxicosis.
TEST RANGE AVAILABLE

14. CLINICAL REFERENCE
 Harrison’s Principles of internal Medicine, 18th Edition
 Guidelines of the American Thyroid Association for the Diagnosis and
Management of Thyroid disease during Pregnancy & Postpartum,
2011
 Tietz Textbook of Clinical Biochemistry, Fifth Edition
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 HYPOTHYROIDISM