The Thyroid Gland is a butterfly-shaped gland found in the lower front part of the neck. Its primary function is to secrete hormones that regulate our metabolic rate, protein synthesis and growth. Despite its harmony, the thyroid gland is sometimes disrupted, leading to excessive thyroid hormone production, a complication known as Hyperthyroidism. These notes will outline the Hyperthyroidism Pathophysiology, but before you read this, make sure that you’ve understood the
Hyperthyroidism Pathophysiology: Causes
The most common cause of Hyperthyroidism in young adults is an AutoImmune Disorder known as Graves Disease, where Thyroid Stimulating Immunoglobins bind to the TSH Receptors and replicate TSH effects. This leads to excess production of thyroid hormones.
On the other hand, the most common cause of Hyperthyroidism in the senior population is Toxic Multinodular Goiter. This condition produces excess thyroid hormones from autonomous ectopic tissue, leading to Clinical Thyrotoxicosis.
Other causes of Hyperthyroidism include:
Iodine-Induced Hyperthyroidism
Thyroid Adenomas
De Quervain Thyroiditis
Postpartum Thyroiditis
Factitious Thyroiditis (misuse of thyroid replacement hormones for weight-loss purposes)
Hyperthyroidism Pathophysiology: Clinical Manifestations
Patients with Hyperthyroidism present with symptoms related to an increase in their metabolic rate and increased oxygen consumption. The initial symptoms include:
Anxiety, restlessness and irritability
Mild hand tremors
Tachycardia
Intolerant to heat and increased sweating
Increased appetite
Diarrhoea
Weight loss
Thinning of their skin
Oligomenorrhea (irregular periods)
Palpable thyroid nodules (in Toxic Multinodular Goiter)
If the cause of Hyperthyroidism is Graves Disease, then patients will also have Pretibial Myxoedema and ocular symptoms, including:
Exophthalmos (Bulging of the eyes)
Decreased blinking
Retracted eyelids
When Hyperthyroidism is left untreated, the symptoms will shift into cardiovascular complications, including:
Sinus tachycardia
Arrhythmias
Decreased cardiac output
Increased pulse pressure
Palpitations
The severity of the symptoms will vary from one individual to another; some might have very mild symptoms that alternate between exacerbations and remissions. While others can experience worsening symptoms that lead to delirium, disorientation, myocardial hypertrophy and heart failure.
Hyperthyroidism Pathophysiology: Medical Treatment
The treatment of Hyperthyroidism is split into two categories. The first category is Symptomatic Therapy, which aims to suppress the symptoms of Hyperthyroidism, such as palpitations, anxiety, and tremors. The treatment of choice for symptomatic therapy is usually Beta-Adrenergic Antagonists, but if the patient has any contraindications, they can be given Calcium-Channel Blockers.
The second category of treatment is the Definitive Therapy which aims to regulate the thyroid hormone level. These include:
Radioactive Iodine Therapy (RAI)
Thionamide Therapy
Subtotal Thyroidectomy
All three definitive therapy approaches have been proven to stop the excess production of thyroid hormones. However, despite their effectiveness, all therapies leave the patients at risk of developing long term hypothyroidism. This means that the patient would need to monitor their T4 levels regularly and possibly take thyroid replacing hormones indefinitely.