Background: Primary hyperparathyroidism is a generalized disorder resulting from excessive secretion of parathyroid hormone involving one or more parathyroid glands. Both familial and sporadic forms exist. Histologic examination reveals parathyroid adenoma in about 90% of patients, although it is sometimes difficult to distinguish an adenoma from a normal gland. Primary hyperparathyroidism is commonly characterized by hypercalcemia, hypophosphatemia and excessive bone resorption.

Methods: This is a case report of a 52-year old female patient with toxic thyroid adenoma and a parathyroid gland adenoma. The patient underwent partial thyroidectomy as a method of choice in treatment of toxic thyroid adenoma. Two years later, clinical hyperparathyroidism caused by an adenoma of parathyroid gland has manifested and was surgically removed.

Conclusions: In mild hypercalcemia, many patients are asymptomatic and this condition is frequently discovered accidentally during routine laboratory screening. In order to provide operative treatment efficiency in thyroid nodule cases, besides thyroid gland morphological diagnostics, it is necessary to perform a preoperative verification of parathyroid glands as well. This diagnostic approach is essential in identifying possible simultaneous occurrence of multiple diseases, such as: thyroid and adenoma of parathyroid gland, in order to diminish incorrect diagnostic estimates.