Hyperthyroidism. Graves-Basedow’s disease (Toxic diffuse goiter)
Hyperthyroidism is elevated activity of the thyroid causing increased levels of T₃ and T₄ in the body, it can cause a hypermetabolic state known as Thyrotoxicosis. Technically, Hyperthyroidism is only one cause of thyrotoxicosis but as it is by far the most common, it is often used interchangeably. Clinical manifestations are:
- Overactivity of the sympathetic nervous system
- Warm, flushed skin with heat intolerance and weight loss (despite increased appetite)
- Stimulation of the gut causing hypermotility, malabsorption and diarrhea
- Palpitations due to tachycardia and a risk of congestive heart failure
- Nervous tremor
- Exophthalmos (only in graves)
- Can lead to thyroid storm - abrupt onset, common in graves, high risk of death from cardiac arrhythmia or heart failure.
Causes are:
- Graves disease (below)
- Multinodular goiter
- Iodine induced hyperthyroidism
- TSH secreting pituitary adenoma
Graves
- Aka toxic diffuse goiter
- Is an autoimmune condition that affects the thyroid and is the most common cause of hyperthyroidism (with a diffuse goiter).
- The body produces antibodies against TSH receptor, they bind to the TSHr and chronically stimulate it, causing continuous production of T₃ and T₄, as the antibodies are basically mimincing TSH.
- Symptoms include rapid pulse, goiter, tremor, exophthalmos, fatigue, weight loss, heat intolerance and palpitations and pretibial myxedema (non-pitting)
- On histology we can see diffuse hypertrophy and hyperplasia of thyroid follicular epithelial cells
H&E, Graves disease: follicles lined by tall columnar cells, some forming papillary infoldings; the colloid is pale with clear vacuoles along its edge (scalloping).
Image: “Graves disease -- intermed mag” by Librepath, CC BY-SA 3.0, via Wikimedia Commons.
Remember: the Graves triad is hyperthyroidism with a diffuse goitre, infiltrative ophthalmopathy (exophthalmos) and infiltrative dermopathy (pretibial myxedema). Microscopy: tall, crowded follicular cells forming papillary infoldings, pale colloid with 'scalloped' edges, and lymphoid infiltrates with germinal centres in the stroma.