Primary hyperparathyroidism as first manifestation in multiple endocrine neoplasia type 2A: an international multicenter study

OBJECTIVE

Multiple endocrine neoplasia type 2A (MEN 2A) is a rare syndrome caused by RET germline mutations and has been associated with primary hyperparathyroidism (PHPT) in up to 30% of cases. Recommendations on RET screening in patients with apparently sporadic PHPT are unclear. We aimed to estimate the prevalence of cases presenting with PHPT as first manifestation among MEN 2A index cases and to characterize the former cases.

DESIGN AND METHODS

An international retrospective multicenter study of 1085 MEN 2A index cases. Experts from MEN 2 centers all over the world were invited to participate. A total of 19 centers in 17 different countries provided registry data of index cases followed from 1974 to 2017.

RESULTS

Ten cases presented with PHPT as their first manifestation of MEN 2A, yielding a prevalence of 0.9% (95% CI: 0.4-1.6). 9/10 cases were diagnosed with medullary thyroid carcinoma (MTC) in relation to parathyroid surgery and 1/10 was diagnosed 15 years after parathyroid surgery. 7/9 cases with full TNM data were node-positive at MTC diagnosis.

CONCLUSIONS

Our data suggest that the prevalence of MEN 2A index cases that present with PHPT as their first manifestation is very low. The majority of index cases presenting with PHPT as first manifestation have synchronous MTC and are often node-positive. Thus, our observations suggest that not performing RET mutation analysis in patients with apparently sporadic PHPT would result in an extremely low false-negative rate, if no other MEN 2A component, specifically MTC, are found during work-up or resection of PHPT.

Effects of mevinolin and mevalonate on cell growth in several transformed cell lines

Studies were conducted to explore the effects of mevinolin, a competitive inhibitor of HMG CoA reductase, on the growth and morphology of normal and transformed murine fibroblasts. Mevinolin is known to block DNA synthesis and cell growth in a number of kinds of non-transformed cells. Eight cell lines were studied, including two normal fibroblast cell lines (C3H 10T 1/2 and NIH 3T3) and derivatives of these cell lines transformed by chemical carcinogens, X-irradiation or the H-ras oncogene. All of the eight cell lines displayed appreciable growth inhibition by 5 microM mevinolin and marked inhibition by 30 microM mevinolin. Mevinolin also induced a marked rounding in the morphology of all of the cell lines. These effects of mevinolin on cell growth and morphology were blocked or reversed by the addition of mevalonic acid. Thus, both normal and transformed cells require mevalonate, or an as yet unidentified metabolite of mevalonate for their growth, even though some transformed cells have become relatively autonomous of other growth factors. Whereas mevinolin acted primarily as a cytostatic agent for most of the cell lines studied, with the transformed cell line MCA/10T 1/2, which ordinarily grows to a very high cell density, prolonged exposure to mevinolin caused marked cytotoxicity. Thus mevinolin might be useful as an anti-tumor agent for specific tumors.