Pathogenesis (development of disease)
In latent (subclinical) hypothyroidism, there is mild dysfunction of the thyroid gland. The thyroid hormones fT3 and fT4 are present in the blood at normal concentrations, whereas TSH (thyroid-stimulating hormone) is > 4 mU/l.
The most common cause of latent hypothyroidism is autoimmune thyroiditis (see below).
Etiology (Causes)
Biographic causes
- Genetic burden/disease
- Ectopic thyroid – anatomical location of the thyroid gland in the wrong place.
- Mutation of the hormone receptors
- Hormonal factors – mutation of hormone receptors.
Behavioral causes
- Nutrition
- Iodine deficiency – people in iodine-deficient areas of Europe are most affected
Disease-related causes
- Autoimmune thyroiditis (AIT; Hashimoto’s thyroiditis) – autoimmune disease of the thyroid gland; initially with increased secretion of thyroid hormones, later with gradual transition to hypothyroidism (hypothyroidism).
- Postpartum thyroiditis (PPT; postpartum thyroiditis) – first occurrence of autoimmune thyroiditis (AIT) up to 12 months after delivery with antibody detection in existing euthyroidism (normal thyroid function).
- Thyroiditis – inflammation of the thyroid gland.
Medication
- Aminosalicylic acid – agent used to treat inflammatory bowel disease such as ulcerative colitis or Crohn’s disease.
- Amiodarone (iodine-containing antiarrhythmic drug).
- Antiestrogens such as aminoglutethimide (aromatase inhibitor).
- Bexarotene (retinoid analog approved for the treatment of cutaneous T-cell lymphoma).
- Iodine
- Lithium
- Thyrostatic drugs, such as carbimazole.
- Inadequate hormone therapy for primary hypothyroidism (hypothyroidism) with L-thyroxine.
- Cytokines such as interferon α
Radiotherapy
- Radioiodine therapy – therapy of hyperthyroidism or thyroid carcinoma with radioactive substances.
- Radiotherapy of the neck region – due to malignant tumors such as malignant lymphoma (malignant lymph node changes).
