Managing hyper- and hypothyroidism in primary care
Roshini Claire Anthony speaks to Dr Adoree Lim, a consultant at the Department of Endocrinology, Singapore General Hospital, on how GPs can help tackle hyper- and hypothyroidism in the primary care setting.
Hyperthyroidism and hypothyroidism can lead to various complications if left untreated. Long-standing hyperthyroidism can lead to, among others, atrial fibrillation, cardiac failure, and osteoporosis, and severe untreated hyperthyroidism (and noncompliance to treatment) puts a patient at risk of thyroid storm.
Untreated hypothyroidism can lead to generalized slowing of the metabolism and multiple cardiovascular complications. In extreme situations, hypothyroidism can result in myxoedema coma, the hallmarks of which are decreased mental status and hypothermia, as well as hypotension, bradycardia, hyponatraemia, hypoglycaemia, and hypoventilation, and patients will exhibit clinical features of severe hypothyroidism such as puffiness of the hands and face, a thickened nose, swollen lips, enlarged tongue, and typical “hung-up” reflexes.
Causes of hyper- and hypothyroidism
Common causes of hyperthyroidism include Graves’ disease, toxic adenoma, or toxic multinodular goitre. More uncommonly, subacute thyroiditis might be a cause of transient hyperthyroidism. The most common cause of hypothyroidism is Hashimoto’s thyroiditis. Some patients may be hypothyroid due to previous treatment with radioactive iodine or surgical thyroidectomy. Occasionally, patients on certain drugs (eg, amiodarone or lithium) may also have hypothyroidism.
The GP should take a thorough history of possible symptoms and perform a physical examination if the patient presents with symptoms that could be related to thyroid conditions, or if the GP notices anything about the patient which could be caused by a thyroid condition.
Some symptoms and physical signs associated with hyperthyroidism include anxiety and nervousness, trembling hands, weight loss, constantly feeling warm, frequent bowel movements, and a fast heart rate. In women, menstrual periods may become irregular. In patients with Graves’ disease, eyes may become more prominent.
Symptoms and physical signs associated with hypothyroidism include constant tiredness, dry skin, hair loss, constipation, leg cramps, and weight gain. In women, menstrual periods may become heavier. However, many of these symptoms are not very specific and may be experienced by otherwise normal individuals.
If there are relevant symptoms and signs, a blood test for the patient’s thyroid function should be obtained. Hyperthyroidism is confirmed by performing a blood test which measures both T4 and TSH levels, where T4 levels would be high and TSH levels very low.
The best way to diagnose hypothyroidism is also with a blood test, where patients would have low T4 and high TSH levels.
The TSH-receptor antibody levels may be tested to diagnose Graves’ disease in patients with hyperthyroidism, while the thyroid peroxidase antibody (TPOAb) will help diagnose Hashimoto’s thyroiditis in patients with hypothyroidism.
Some symptoms of thyroid conditions are non-specific and may therefore overlap with other diagnoses. As such, it is important to take a detailed history and perform a thorough physical examination to look for evidence that supports the diagnosis of a thyroid condition.
Routine screening is probably unnecessary. However, there are certain patients who might be at a higher risk for thyroid conditions (ie, patients with a history of other autoimmune conditions such as type 1 diabetes or patients with a very strong family history of thyroid diseases).
Hyperthyroidism may be treated with either carbimazole or propylthiouracil. The dose given is usually dependent on the initial level of thyroid hormones. As the condition improves (and depending on the underlying cause of hyperthyroidism), the dose of the medications should be decreased according the patient’s symptoms and thyroid function tests.
Hypothyroidism should be treated with levothyroxine replacement. The dose of levothyroxine will vary from patient to patient and should be adjusted according to the patient’s symptoms and thyroid function tests.
Patients with Graves’ disease may be treated with antithyroidal medications for 12–18 months and reassessed after that. Some of these patients may no longer need further treatment whereas others may relapse and may need referral for definitive treatment in specialist care. Patients with hypothyroidism will usually require lifelong thyroxine replacement.
Surgery may be necessary in a patient with Graves’ disease who has previously relapsed but does not want radioactive iodine as a treatment option. Thyroid surgery involves removing most of the thyroid gland. This is an effective treatment for hyperthyroidism, and is particularly recommended if the goitre is very big and cosmetically unattractive. Surgery is also carried out if there is a concern about thyroid cancer.
GPs should refer the patient to a specialist whenever they feel that they are not comfortable with the patient’s progress. In particular, some cases of Graves’ disease, especially the ones who have previously relapsed or have high antibody levels, may be more difficult to treat and may need specialist input or further treatment, such as radioactive iodine, which is only available at tertiary hospitals.
There are specific conditions that should definitely be managed by a specialist. Patients whose thyroid function tests do not fall into the typical pattern of either primary hyperthyroidism or hypothyroidism should be sent to a specialist for further evaluation. Patients diagnosed with thyroid conditions and who later become pregnant should also be sent for further specialist care. Patients who have a constellation of autoimmune conditions should also be sent to the specialist.
While we do not have data on the prevalence of all thyroid conditions in Singapore, it is fair to say that thyroid problems are relatively common and we expect their prevalence in Singapore to be fairly similar to that of other developed countries. As such, it is helpful to have a good knowledge of how to manage the more straightforward cases in the primary care setting.
American Thyroid Association
British Thyroid Association
American Family Physician