Thyroid autoimmunity in hyperprolactinaemic disorders

Abstract

Abstract. Circulating thyroglobulin antibodies (TgAb) and microsomal antibodies (MsAb) and thyroid function (total and free T4 and T3, TSH basal and after TRH) have been evaluated in 92 hyperprolactinaemic patients (82 females and 10 males; 9 with macroprolactinoma, 22 with microprolactinoma, 4 with acromegaly, 5 with organic lesions of the hypothalamus, 2 with empty sella, 2 with idiopathic hypopituitarism, 2 with primary hypothyroidism, and 46 with idiopathic hyperprolactinaemia). Thyroid function was normal in all cases except 3 with hypothalamic disease and central hypothyroidism, the 2 patients with primary hypothyroidism and 2 with thyrotoxicosis (one due to Graves' disease and one to autonomous thyroid adenoma). High titres of TgAb (≥1/1250) and/or MsAb (≥ 1/1600) were found in the subject with Graves' disease, in one acromegalic, in the 2 primary hypothyroids, and in 12 women with either adenomatous or idiopathic hyperprolactinaemia; low titres of one or both antibodies were found in 9 other euthyroid women and in the one with toxic adenoma. In a control population of 185 subjects studied with the same methods, the prevalence of TgAb and/or MsAb positive (low titres) was 3.3% in females and 2.5% in males. Diffuse thyroid hyperplasia was clinically detectable in 12 euthyroid women and in the one with Graves' disease; 3 others had been previously operated for nodular goitre with histological evidence of Hashimoto's thyroiditis (2 cases) or for a cold nodule; a single thyroid nodule was present in the woman with toxic adenoma and in one euthyroid woman. Most of these subjects also had circulating TgAb and/or MsAb, and a few had increased TSH secretion. No significant differences were found in mean thyroid hormone and TSH levels between euthyroid hyperprolactinaemic subjects and healthy controls, but TRH-stimulated TSH levels were significantly higher in thyroid antibodies positive than negative subjects. These data, in agreement with a few previous reports, suggest that autoimmune thyroid disorders (especially asymptomatic autoimmune thyroiditis) occur in hyperprolactinaemic women with a prevalence far exceeding that observed in many surveys in the general population.