Thyroid disease is common in women, and general practitioners are well placed to diagnose and manage most cases. Hypothyroidism is the most frequent thyroid disorder, affecting an estimated 5–10% of Australian women, with prevalence increasing with age. Hyperthyroidism is less common, seen in around 1–2% of women.
Early recognition is crucial. Hypothyroidism often presents insidiously with nonspecific symptoms such as fatigue, weight gain, cold intolerance, dry skin, constipation, and menstrual irregularities. Given the overlap with conditions like depression and menopause, thyroid dysfunction should always be considered in women presenting with these complaints. Hyperthyroidism may manifest as anxiety, palpitations, tremor, heat intolerance, weight loss, or menstrual disturbance. It is important to consider overlapping or co-existing conditions such as depression and menopause, which can also present with similar symptoms.
Initial investigations include measuring thyroid-stimulating hormone (TSH) and free thyroxine (FT4). Primary hypothyroidism is characterised by an elevated TSH with a low FT4. The most common cause of primary hypothyroidism is autoimmune thyroiditis (Hashimoto’s), confirmed by the presence of anti-thyroid peroxidase antibodies (anti-TPOAbs).
Management of hypothyroidism involves levothyroxine replacement, titrated to normalise TSH levels, with adjustments every 6–8 weeks. Patients should be advised that symptom resolution may take several months, and annual review is essential. Subclinical hypothyroidism (raised TSH, normal FT4) may require treatment if TSH exceeds 10 mIU/L, if the patient is symptomatic, or if planning pregnancy.
Hyperthyroidism is diagnosed when FT4 is elevated and TSH is suppressed. The most common cause is Graves’ disease, characterised by elevated thyroid receptor antibodies (TRAb). Other causes include toxic multinodular goitre, toxic adenoma, and postpartum thyroiditis. Additional tests, such as thyroid receptor antibodies (TRAb) or radionuclide uptake scans, can distinguish Graves’ disease from thyroiditis or nodular disease. First-line treatment for Graves’ disease typically involves antithyroid drugs (carbimazole or propylthiouracil) for 12–18 months. Radioactive iodine or surgery may be considered in cases of relapse or contraindications to medical therapy. Postpartum thyroiditis is relatively common, affecting up to 10% of women within a year of childbirth. It often follows a transient hyperthyroid phase, usually managed symptomatically with beta blockers, and may progress to hypothyroidism requiring temporary levothyroxine. Regular monitoring is crucial for identifying resolution and screening for longer-term dysfunction.
Thyroid disorders can significantly impact fertility and pregnancy outcomes. Both hypo- and hyperthyroidism are associated with subfertility, miscarriage, and preterm delivery. Women should therefore be counselled on the importance of optimising thyroid function pre-conception. Discussing contraception during routine thyroid reviews may help facilitate planned pregnancies. During pregnancy, levothyroxine requirements often increase by up to 50%, necessitating closer monitoring.
Thyroid disease is common and disproportionately affects women. GPs play a crucial role in early detection, investigation, patient education, and long-term management, ensuring that women understand the importance of treatment adherence, regular monitoring, and pregnancy planning. With a proactive, patient-centred approach, women with thyroid disease can expect to lead healthy lives with good reproductive outcomes.
Dr Samantha Miller, MBChB
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