Paediatrics: Hyperthyroidism (thyrotoxicosis)

Hyperthyroidism (thyrotoxicosis)

• Thyrotoxicosis: refers to the clinical, physiological, and biochemical findings that result when the tissues are exposed to excess thyroid hormones.
• Hyperthyroidism: denotes those conditions resulting in hyperfunction of the thyroid gland leading to a state of thyrotoxicosis.

Causes of thyrotoxicosis

Due to hyperthyroidism

• Excessive thyroid stimulation:
• Graves’s disease
• Hashimoto’s disease
• neonatal (transient) thyrotoxicosis
• pituitary thyroid hormone resistance (excess TSH)
• McCune–Albright syndrome
• hCG-secreting tumours
• Thyroid nodules (autonomous):
• toxic nodule/multinodular goitre
• thyroid adenoma/carcinoma

Not due to hyperthyroidism

• Thyroiditis:
• subacute
• drug-induced
• Exogenous thyroid hormones

Clinical features (all causes)

Thyrotoxicosis may be associated with the following symptoms:

• hyperactivity/irritability;
• poor concentration; altered mood; insomnia;
• heat intolerance/fatigue/muscle weakness/wasting;
• weight loss despite increased appetite;
• altered bowel habit—diarrhoea;
• menstrual irregularity;
• sinus tachycardia; increased pulse pressure;
• hyperreflexia; fine tremor;
• pruritis.

Investigations

•  Thyroid function tests (serum): raised T4 and T3; suppressed TSH.
• Thyroid antibodies: antithyroid peroxidase; anti-thyroglobulin; TSH receptor antibody (stimulatory type).
• Radionucleotide thyroid scan: increased uptake (Graves’s disease); decreased uptake (thyroiditis).