Goitre or Goiter
Goiter refers to an abnormal swelling of the thyroid gland. It can be diffuse or nodular, depending on the cause, and may be associated with normal, decreased, or increased thyroid hormone production.
It is spelled ‘goitre’ in British English and ‘goiter’ in American English.
Endemic Goitre
This is a visible enlargement of the thyroid gland occurring due to dietary iodine deficiency. Patients are usually euthyroid. Areas endemic for iodine deficiency are those where soil is poor in its iodine content as in mountain bases.
Iodine Deficiency Disorders
Abbreviated as IDD, this includes endemic goitre, cretinism/congenital hypothyroidism, and adult hypothyroidism. It is the commonest preventable cause of physical and mental retardation in the world.
Euthyroidism
This is a state in which there is normal production of thyroid hormone.
Hyperthyroidism and Thyrotoxicosis
Thyrotoxicosis is the clinical and biochemical syndrome occurring due to excess thyroid hormone. The term hyperthyroidism should be used only to denote thyrotoxicosis due to hyperfunction of the thyroid gland itself. Many, however, consider these two terms interchangeable. Typically, serum T4 and T3 are elevated and TSH level is suppressed. Common causes include Graves’ disease, multinodular toxic goitre and solitary toxic nodule.
Thyrotoxicosis Factitia
This is ‘faked’ thyrotoxicosis due to unprescribed intake of thyroxine pills by euthyroid persons.
Struma ovarii
This is an ovarian teratoma containing hyperfunctioning thyroid tissue.
Hypothyroidism
This is an endocrine disorder resulting from a deficiency of thyroid hormone. Commonest causes are Hashimoto’s thyroiditis, atrophic thyroiditis, and iodine deficiency. Typically, serum T3 and T4 are low while TSH is elevated.
Primary hypothyroidism is hypothyroidism characterized by decreased thyroxine production by the thyroid gland with a high serum thyroid-stimulating hormone concentration. It accounts for over 95 percent of cases of hypothyroidism.
Central hypothyroidism is characterized by a low serum T4 concentration and a serum TSH concentration that is low or not appropriately elevated. Central hypothyroidism is caused by either hypothalamic (tertiary hypothyroidism) or pituitary (secondary hypothyroidism) disease.
Cretinism
Cretinism is a clinical syndrome caused by severe hypothyroidism in an infant or child.
Congenital Hypothyroidism
This is due to inadequate thyroid hormone production in newborn infants. It can occur because of an anatomic defect in the gland, an inborn error of thyroid metabolism, or maternal iodine deficiency and is the most common neonatal endocrine disorder.
Subclinical Hypothyroidism
This is defined biochemically as normal serum T3 and T4 concentrations with elevated serum TSH. Its management is guided by the degree of elevation of TSH, the patient’s symptoms, and the presence of thyroid antibodies.
Subclinical Hyperthyroidism
This is characterized by a suppressed serum TSH level with normal T3 and T4 levels. Patients may have few or no symptoms of hyperthyroidism.
Gestational Hyperthyroidism
This is a transient thyrotoxicosis caused by stimulation of thyroid gland by HCG and usually limited to the first 12-16 weeks of pregnancy. It occurs especially in women with hyperemesis gravidarum.
Hashimoto’s Thyroiditis
This is the most common cause of hypothyroidism in iodine-sufficient areas. It is caused by an autoimmune destruction of the thyroid with marked lymphocytic infiltration of the gland.
Atrophic Thyroiditis
This is an autoimmune disease is characterized by extensive fibrosis within the thyroid gland. It usually represents the end of Hashimoto’s thyroiditis though it may occur as a separate disorder.
Graves’ Disease
It accounts for 60 to 80% of thyrotoxicosis and is an autoimmune disease influenced by genetic and environmental factors. The excessive thyroxine production is caused by thyroid-stimulating immunoglobulin.
Apathetic Thyrotoxicosis is a clinical form of hyperthyroidism in the elderly that manifests with weakness and no symptoms of sympathetic overactivity.
Graves’ Ophthalmopathy
This is an autoimmune inflammatory disorder of the orbit and periorbital tissues, characterized by upper eyelid retraction, lid lag, orbital swelling, enlarged extraocular muscles, and exophthalmos. It can precede or follow the onset of Graves’ disease and uncommonly may occur without hyperthyroidism.
Thyroid Dermopathy/Pretibial Myxoedema
This is an infiltrative skin condition occurring only in Graves’ disease and manifesting as hyperpigmented, violaceous, orange-peel textured papules typically occurring on the shins.
Thyroid Acropachy
This is clubbing associated with periosteal new bone formation in the metacarpal bones and phalanges occurring in Graves’ disease.
Myxoedema Coma
This is an endocrine emergency due to severe hypothyroidism. It is characterized by obtunded mental status, hypothermia, and slowing of function in multiple organs.
Thyroid Storm
Also referred to as thyrotoxic crisis, this is an acute, life-threatening hypermetabolic state induced by excessive release of thyroid hormones in persons with thyrotoxicosis.
Sick Euthyroid Syndrome
This is defined by abnormal findings on thyroid function tests that occur in the setting of acute nonthyroidal systemic illnesses. Common serum findings are low T3, low T4, and normal or low TSH.
de Quervain’s Thyroiditis
Also known as subacute viral thyroiditis, this is an inflammatory viral condition characterized by anterior neck pain and a tender thyroid gland. Hyperthyroidism is typically the presentation followed by euthyroidism, hypothyroidism, and ultimately restoration of normal thyroid function.
Reidel’s Thyroiditis
This is a rare, chronic inflammatory disease of the thyroid gland characterized by a dense fibrosis that replaces normal thyroid parenchyma.
Postpartum Thyroiditis
This is an autoimmune thyroid disease that occurs during the first year after delivery. Women may present with transient thyrotoxicosis alone, hypothyroidism alone, or transient thyrotoxicosis followed by hypothyroidism. Some may develop permanent hypothyroidism.
Solitary Thyroid Nodule
The term defines itself. Single nodules are more likely to harbour malignancy than multiple thyroid nodules. Single nodules in children are more likely to be malignant than those in adults.
Solitary Toxic Nodule
This is an autonomously hyperfunctioning single thyroid nodule that causes hyperthyroidism.
Multinodular Toxic Goitre
Also known as Plummer’s disease, this cause of thyrotoxicosis is characterised by multiple autonomously functioning nonmalignant nodules.