Presentations
of hyperthyroidism include heat intolerance, anxiety, palpitations,
tremor, weight loss, fatigue, tachycardia, irregular periods, lid lag...
Possible causes to consider include:
1) Graves disease
Graves’ disease is the commonest cause and is autoimmune-mediated. In around 30% of patients this diagnosis may be apparent by the presence of exophalthmos/complaints of diplopia. The danger of this is optic nerve compression, which presents as blurred vision/decreased VA, or decreased colour vision. More rarely thyroid acropachy (clubbing) or pretibial myxoedema may be present. There is diffuse, non-tender swelling of the thyroid. Blood tests may reveal positive thyroperoxidase antibodies and/or thyroglobulin antibodies – but these are not specific and are also found in hashimotos. TSH receptor antibodies are specific. There is also raised thyoid stimulating immunoglobulin. A radioactive iodine scan would reveal diffuse increased uptake.
2) Toxic multinodular goitre
Toxic multinodular goitre, AKA Plummers disease, refers to benign thyroxine-secreting tumours. Thyroperoxidase antibodies are negative and a radioactive iodine scan shows normal or increased radioactive iodine uptake with focal areas of uptake.
3) Toxic nodule
Like multinodular goitre but a singular benign tumour and hence the normal/increased radioactive iodine uptake is all in one area.
4) Excess throxine ingestion
This will result in low serum thyroperoxidase and low to undetectable radioactive iodine uptake
6) Postpartum thyrotoxicosis
Postpartum thyrotoxicosis affects 10% females within 6 months of birth. It is caused by autoimmune lympocytic infiltration of thyroid and has positive thyroperoxidase antibodies. It is painless and resolves spontaneously.
( 7) Subacute thyroiditis
Subacute thyroiditis, AKA de Quervain thyroiditis, is thought to be a complication after a viral illness. Patients have tender, enlarged thyroids, often associated with a fever. They may have weakly positive thyroid antibodies. There is low radioactive iodine uptake. Recovery is usually spontaneous and treatment is to give NSAIDS. )
Treatment of hyperthyroidism
1) Thionamides – carbimazole, propylthiouracil
- Induce remission in 60% of Graves patients in a year
- Not appropriate for long term treatment of toxic nodular goiter as it rarely remits
- Side effects: commonly rash, fever, urticaria, arthralgia, mild rise in transaminases (30%); rarely agranulocytosis (0.5%), vasculitis or hepatitis.
- In pregnancy use propylthiouracil over carbimazole
2) Radioactive iodine
- reduces goiter size by 40%
- eventually causes hypothyroidism in almost all patients
- may cause Graves’ opthalmopathy to worsen, especially in smokers – give glucocorticoids at same time
3) Thyroidectomy
- causes hypothyroidism in most patients
- treat with thionamides and Lugols solution first
Small print gem: HCG
is a weak thyroid stimulator so rarely molar pregnancy, choriocarcinoma
or hyperemsis gravidarum can cause transient hyperthyroidism.
