Academic literature on the topic 'Thyroid gland diseases - drug therapy'

Graves’ disease (GD) is one of the most common autoimmune conditions in women of reproductive age. The disorder is characterized by the presence of pathogenic immunoglobulins that bind the TSH receptors (TRAbs) and stimulate the production of thyroid hormones leading to hyperthyroidism (the occurrence of inhibiting or neutral antibodies being rare). Affected individuals can be treated by radioiodine therapy, surgical removal of the gland or by antithyroid drugs (ATDs). Thyroid stimulating immunoglobulins may persist for years after medical treatment, radioiodine therapy or surgical removal of the gland in those affected by GD and during pregnancy can cross the placenta and can act on the fetal thyroid gland resulting in the development of fetal and neonatal hyperthyroidism and sometimes to goiter. Antithyroid drugs used during pregnancy can also cross the placenta and may be teratogenic and act on the fetal thyroid gland, leading to fetal and neonatal hypothyroidism and goiter. This chapter will discuss specific aspects of GD during pregnancy and postpartum focusing on fetal and neonatal consequences related to this disorder.

Radioactive iodine has been used successfully for almost 70 years since the first treatment took place at the Massachusetts General Hospital in Boston in 1941. However, it was not until after the Second World War that ¹³¹I became generally available for clinical applications (1). The radioactive iodine isotope is chemically identical to ‘stable’ iodine (¹²⁷I) and thus becomes a part of the intrathyroidal metabolism. Its principle of action is based on the emission of β‎-rays with a range of 0.5–2 mm in the tissue leading to high local radiation absorbed doses while sparing surrounding structures. The additional γ‎-ray component of ¹³¹I allows for scintigraphic imaging of the distribution in the gland and can also be used for pre- and post-therapeutic individual dosimetry (see below). Several therapeutic options are available for the treatment of benign thyroid disorders, namely hyperthyroidism: surgical resection (hemithyroidectomy, near-total, or total thyroidectomy), long-term antithyroid drug medication (ATD), and radio-iodine therapy (RAIT) (2, 3). These different treatment modalities are used in varying frequencies depending on geographical location, e.g. iodine supply, availability and logistics, cultural background, and patient-specific features, e.g. goitre size, presence of local symptoms, age, and hormonal status. The diversity of approaches on an international scale still remains impressive and is reflected by a great heterogeneity throughout Europe and also when compared to the USA where radio-iodine therapy is still being applied more frequently than in most European countries (4–8). Radio-iodine therapy was originally aimed at eliminating hyperthyroidism and thus leaving the patient euthyroid. Up-to-date strategies, however, established postradio-iodine induction of hypothyroidism as the treatment objective and, thus, it is included in the category of ‘cure’. This definition holds especially true for the management of Graves’ disease when long-term hypothyroidism was the rule and stabilization of euthyroidism failed in the majority of cases. In fact, the term ‘ablation’, meaning removal or destruction, has been increasingly used to characterize radio-iodine therapy and administration of larger amounts of radio-iodine have tended to make this a self-fulfilling prophecy. Although many clinicians prefer that the end result of treatment be the more easily managed hypothyroidism, others are still reluctant to give up the therapeutic ideal of euthyroidism as the preferred result of radio-iodine therapy and continue their efforts to solve the enigma of thyroid radiosensitivity.

Chapter 81 discusses thyroid diseases. Thyroid hormone is a regulator of normal physiology, including normal function of the musculoskeletal system. The most important causes of both elevated thyroid hormone levels (hyperthyroidism) and decreased hormone levels (hypothyroidism) are diseases of the thyroid gland. These are primarily diagnosed using serum testing and thyroid imaging. Muscle weakness is a common musculoskeletal complaint in both hyperthyroidism and hypothyroidism. In adults, osteoporosis is often evaluated in hyperthyroid patients using DXA, however, other musculoskeletal manifestations are often incidentally detected. Treatment options include radioactive iodine ablation of the thyroid gland, medical therapy, and surgery.

The hypothalamus–pituitary–thyroid–periphery (HPTP) axis has been known to be a vulnerable target for environmental factors and nutritional agents for centuries. Goitrogenesis, hypo- and hyperthyroidism, tumorigenesis, and autoimmune diseases of this gland have been linked to single or combined deficiencies of several essential trace elements. Normal thyroid function depends on adequate and balanced availability of the essential trace elements iodine, selenium, iron, and the mineral zinc in the daily diet. It has been suggested that the evolution of humankind and Eve’s route of migration out of Africa, to displace the Neanderthal people and to populate the other continents, closely followed coastlines and regions with high availability of iodine, the key element required for thyroid hormone synthesis (1, 2). Involuntary or voluntary environmental or nutritional exposure to adverse factors and agents impairing thyroid hormone synthesis, secretion, binding, transport, metabolism, and action (‘goitrogens’) contributes to the development and persistence of thyroid disorders (3). Iodine deficiency, still prevalent in many regions of our world, and iodine excess (4), both of which might occur during embryonal and fetal development as well as in newborns, adolescents, and adults, provide the platform for action of adverse agents, which might be well tolerated by a normally functioning ‘quiescent’ thyroid gland with adequate iodine supply (see Chapters 3.2.3, 3.2.4). Compounds adversely affecting the HPTP axis belong to several chemical classes of food ingredients and environmental contaminants, but might also represent pharmaceutical drugs acting either directly on biomolecules comprising the HPTP axis or after modification by phase I and/or II drug metabolism (see Table 3.2.2.1). Apart from by ingestion, several agents reach their targets after inhalation (e.g. occupational exposure or smoking) or by dermal application (e.g. UV screens).