Retrospective analysis of the association of nodular goiter with primary and secondary hyperparathyroidism.

Background: The association of hyperparathyroidism (HPT) with thyroid disease has long been known, but the mechanisms underlying such an association have not yet been clarified.

Objective: To elucidate the main factors determining this combination of endocrine diseases, in a retrospective multicenter study.

Methods: We retrospectively reviewed all patients referred for parathyroid scintigraphy in the period 1990-1999. A total of 487 patients in the age range 17-65 years were selected for the analysis (339 women and 148 men); group A included 241 patients with primary and group B 246 patients with secondary HPT.

Results: A total of 124/241 patients in group A (51.5%), but only 92/246 patients in group B (38.2%) had thyroid disorders (notably nodular goiter) associated with HPT (P=0.0035). Thyroid disorders were evenly distributed throughout the entire 17-65 years age range in group A, but 17-40-year-old patients in group B had significantly fewer thyroid disorders than the older patients of the same group (15.5% compared with 43.3%, P<0.002), as expected in a general population. In patients with primary HPT there was no difference in the prevalence of thyroid disease between women and men, whereas the ratio of women to men in secondary HPT patients with thyroid disease was about 3:1.

Conclusions: These results demonstrate an increased prevalence of nodular goiter in patients with primary rather than secondary HPT, and are consistent with a possible role of increased endogenous calcium concentrations (a hallmark of primary, but not of secondary, HPT) as a goitrogenic factor in patients with HPT.