The normal thyroid gland consists of two lobes joined by an isthmus in the middle. Thyroid gland is located in the front of your neck. The thyroid gland synthesizes two hormones, T3 and T4, from iodine taken in the diet. Production of T3 and T4 in the thyroid is controlled by a mechanism called feedback mechanism. T3 is the metabolic active hormone which acts as a stimulus. Thyroid hormones control the general metabolism by regulating the rate of oxidation and production of energy. They maintain the basal metabolic rate of the body. They promote growth of body tissues and development of mental functions during infancy and childhood. They sensitize the tissues to the action of endogenous catecholamine. Therefore excess of these hormones lead to symptoms and signs of sympathetic stimulation characteristically seen in hyperthyroidism
What is Hyperthyroidism?
Hyperthyroidism is a clinical syndrome that results from exposure of the body tissues to excess of circulating free thyroid hormones. Hyperthyroidism also called as thyrotoxicosis. Thyrotoxicosis literally means toxicity due to excess of thyroid hormones. All the tissues that contain thyroid receptors are affected. Hyperthyroidism affects females more than males and is usually associated with thyroid enlargement.
What Are The Causes Of Hyperthyroidism?
The causes of hyperthyroidism are
- Graves disease:-
It is the most common thyroid disorder producing hyperthyroidism. It is characterized by the symptoms that are diffuse goiter, exophthalmos and pre-tibial myxedema. It can occur at any age but is common between 30-50 years old age group. It is an autoimmune disorder. Normally in an autoimmune disorder, antibodies destroy the thyroid tissue but this is an exception where the thyroid IgG antibodies stimulate the thyroid to produce more hormones. Exophthalmos is due to collection of retro-orbital fluid and proliferation of fibroblasts which lead to rise in pressure in retro-orbital space, which pushes the eyeballs forward.
- Toxic nodular goiter:- multinodular and solitary nodule
- Excess iodine:- high amount of iodine can cause hyperthyroidism. Iodine is used by the body to produce hormones.
- Thyroid medication:- taking too much thyroid hormone medication can cause hyperthyroidism. Don’t increase the dose of thyroid medication without consulting your doctor. Don’t take more doses than prescribed.,
- Less common causes are thyroiditis, thyroid carcinoma
What are the Symptoms of Hyperthyroidism?
Moderate to severe hyperthyroidism produces characteristic features, the presentation of which varies from patient to patient. The clinical symptoms and signs are due to
- Accelerated basal metabolic rate
- Stimulation of sympathetic system due to hypersensitisation
- Compressed due to enlarged thyroid
There are different modes of presentation at different age groups. A child may present with behavioural abnormalities or premature growth spurt or deterioration of mental functions. An old man may present with irregular heartbeats. Sometimes symptoms and signs may not be complained of but can be observed at clinical examination
Goiter:- diffuse or nodular. Diffuse goiter indicates Graves disease while nodularity indicates toxic nodular goitre
- Gastrointestinal:- weight loss in spite of good appetite, diarrhea, vomitings
- Cardiovascular:- high resting pulse rate, irregular heart beat
- Neuromuscular:- nervousness, irritability, restlessness, psychosis, tremors of hands, muscular weakness, exaggerated tendon reflexes
- Dermatological:- increased sweating, clubbing of fingers, redness of palms, hair loss
- Reproductive:-menstrual irregularity, abortions, infertility, impotence
- Ophthalmological:- lid lag or lid retraction, staring look, excessive watering of eyes, double vision
- Other symptoms are heat intolerance, excessive thirst, outburst of anger, fatigability
- Antithyroid drugs:- the Antithyroid drugs block the iodination of tyrosine, hence, reduce the synthesis of thyroid hormones. Carbimazole is commonly used drug
- Radioactive ablation of thyroid:– hyperactive thyroid gland is destroyed by radioactive iodine. Indications for this treatment are patients more than 40 years of age, recurrence following surgery.
- Subtotal thyroidectomy:– indications for subtotal thyroidectomy are
- Large goiter
- Frequent relapses on drug treatment
- Age less than 40 years with thyrotoxicosis hypersensitive to drug therapy
- Poor drug compliance.
Hyperthyroidism Treatment in Pregnancy:-
The hyperthyroidism in pregnancy is always due to grave’s disease. Antithyroid drugs cross the placental barrier; hence, there is risk of fetal hypothyroidism. As a general rule, dosage of Antithyroid therapy should be the lowest effect does necessary to control hypothyroidism during pregnancy. Betablockers should not be used as an adjuvant therapy during pregnancy because of their effect on fetus. Radioactive iodine is contraindicated during pregnancy and subtotal thyroidectomy is not6 preferred over drug treatment if patient is responsive to therapy.