Question

Describe tests in the diagnosis and management of thyroid disorders. Explain the conditions of hyper- and hypothyroidism. Then, describe how each test or measure could be used to diagnose the condition.

Answer 1

Diagnostic tests in thyroid disorders:

Thyroid disorders are the common endocrine disorders that affects 10% US population. The main disorders of Thyroid are Hypothyroidism and hyperthyroidism. There are various tests that can be performed in the diagnosis  and management of Thyroid disorders. The most commonly used tests are blood tests for thyroxine, triiodothyronine , TSH , TSH receptor Antibodies, Thyroglubulin , Thyroglobulin Antibodies , Thyroid perioxidase Antibodies etc.

Hyperthyroidism

It is a pathological condition resulting from the excessive production of thyroid hormones. Increased thyroxine level , as a result of Hyperthyroidism, can increase the metabolism in the body. Hyperthyroidism is characterised by rapid or irregular heartbeat, sweating, unexpected weight loss, irritability etc. The main cause for Hyperthyroidism is an autoimmune disorder, called Graves' disease. In Graves' disease, antibodies produced by immune system stimulates the thyroid gland to produce hormones in excessive amount. Other disorders include thyroiditis, too much intake of iodine, tumours of thyroid etc.

Hypothyroidism

The disease state caused by insufficient production of thyroid hormones by the thyroid gland, is called Hypothyroidism. It is characterised by cold sensitivity, constipation, fatigue, weight gain , thinning of hair , slowed heart rate, muscle weekness and aches, and dry skin. Hypothyroidism can be caused due to Hashimoto's disorders, an autoimmune disorder, over response of Hyperthyroidism treatment , surgeries on thyroid or due to medications like lithium in mood disorders.

Tests for the Diagnosis and Management of Hyperthyroidism and Hypothyroidism :

1. Blood test for:

* Thyroxine and triiodothyronine: These are the two main hormones produced by the thyroid gland. Free Thyroxine ( FT4) normal value is 0.7 to 1.9ng/ dl. Triiodthyronine ( T3) is 80 - 180 ng / dl. Elevated level of T3 and T4 indicates hyperthyroidism and below normal level of T4 and T3 indicates Hypothyroidism.

* TSH level: Thyroid Stimulating Hormone is produced by Anterior Pituitary gland to stimulate the thyroid to produce hormones. Increased TSH level indicates the insufficient production of thyroid hormones ( as the TSH production is regulated by negative feedback mechanism from T3 and T4). TSH normal level is 0.4 to 4 mU/ L.

TSH above 4 mU/L along with low T4 level indicates Hypothyroidism.

* Antibodies against thyroid indicates Autoimmune disorders. These antibodies and its normal ranges are:

TSH receptor Antibody( TRab): 1.75 IU / L or less.

Thyroid Stimulating Immunoglobulin Antibody ( TSI): Below 140% of basal activity.

Thyroglobulin antibody ( TgAb): > 20 IU/mL

Thyroid Perioxidase Antibody( TPO Ab): >35 IU / mL.

Elevated levels of these Antibodies suggest the presence of Autoimmune disorders. This antibodies are producing against the thyroid Antigens. Elevated levels of TPOAb indicates mainly the presence of Hashimoto's disease.

Elevated Serum TSI level mainly indicates the Graves disease.