Can I get pregnant with subclinical hyperthyroidism?

Subclinical hyperthyroidism and hyperthyroidism are not the same disease, but the causes of the two are extremely similar. Patients often show myocardial damage and arrhythmias, and some patients also show mild mental symptoms. From a clinical perspective, patients with subclinical hyperthyroidism can become pregnant, but it is best to start preparing for pregnancy when all levels are normal, otherwise it will affect the normal development of the fetus.

1. Causes

The pathogenesis of subclinical hyperthyroidism is similar to that of hyperthyroidism. Epidemiological data show that the incidence of hyperthyroidism increased after iodine supplementation in iodine-deficient areas. It is considered that these patients may have been in subclinical hyperthyroidism due to iodine deficiency before iodine supplementation, and showed clinical hyperthyroidism after iodine supplementation; for example, for patients with hypothyroidism, overly aggressive thyroid hormone replacement therapy, or excessive thyroid hormone during TSH suppression therapy for patients with thyroid cancer; in patients with functional autonomous nodules, subclinical hyperthyroidism may also be induced by the increase of exogenous iodine load such as radiocontrast agents, amiodarone or other iodine-containing drugs and seaweed.

2. Clinical manifestations

Subclinical hyperthyroidism is usually asymptomatic, but long-term follow-up has found that subclinical hyperthyroidism can cause myocardial damage, arrhythmias, and affect bone metabolism. Some patients may experience mild mental symptoms and signs.

1. Heart damage

(1) When at rest, diastolic perfusion is impaired, while during activity, left ventricular ejection fraction increases and exercise tolerance decreases significantly. There may be some improvement after treatment with β-adrenergic receptor blockers.

(2) Accelerated heart rate, atrial arrhythmias, and premature contractions.

(3) Echocardiography may reveal left ventricular hypertrophy.

2. Abnormal bone metabolism

Women are at high risk of bone density loss in the early postmenopausal period, so both subclinical hyperthyroidism and overt hyperthyroidism will increase postmenopausal osteoporosis. In patients with clinical hyperthyroidism, increased bone resorption may cause hypercalcemia, but more commonly there is a decrease in bone density, with cortical bone being more severely affected than trabecular bone.

There are no definite reports on the effects of subclinical hyperthyroidism on bone metabolism in premenopausal women and men.

3. Can I get pregnant with subclinical hyperthyroidism?

Can you get pregnant with subclinical hyperthyroidism? Thyroid function during pregnancy has its particularities. The requirement for thyroid hormone increases by 30-50% during pregnancy. In the first half of pregnancy, the thyroid hormone that the fetal brain development depends on comes entirely from the mother. If TH is too high, you can take a small dose of Euthyrox orally as a replacement therapy to maintain normal FT3 and FT4, and TH should be below 2.5. If TH is slightly lower, or FT3 and FT4, which play a physiological role, are not reduced, it will generally not affect the fetus.