Primary hyperaldosteronism is associated with other endocrinology pathologies, like pheochromocytoma, Cushing's syndrome, hyperprolactinemia, primary hyperparathyroidism and a type of multiple endocrine neoplasia. Furthermore, association between hyperaldosteronism and thyroid diseases were already pointed out. Aim of the study was to value the prevalence of some thyroid diseases in a series of patients with primary hyperaldosteronism. We studied 105 consecutive patients with primary hyperaldosteronism, 43 (40.95%) with adrenal adenoma, 62 (50.05%) with bilateral adrenal hyperplasia and a control group of 223 patients with essential arterial hypertension. In all patients we tested thyroid function (FT3, FT4, TSH), thyroid antibodies (AbTPO, AbTG) and, sometimes, thyroid morphology by ultrasonography (US scan). The results of the study show that thyroid disfunction occur in 28.6% of patients with primary hyperaldosteronism and in 16.6% of patients with essential hypertension, with a statistically significative difference (chi2 = 0.012). At present, the relationship between primary hyperaldosteronism and thyroid diseases is unclear, but it can be hypothesized that there are common pathogenetic mechanisms, like an imbalance between various growth factors. Further studies are necessary to confirm the results of our study.