Thyroid cysts: a new extra-adrenal site of aldosterone synthase expression and increased aldosterone content

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Thyroid cysts: a new extra-adrenal site of aldosterone synthase expression

and increased aldosterone content

Yona Greenman*, Yana Trostanetsky*, Sarit Ben-Shemen*, Nili Grazas

<http://www3.interscience.wiley.com/journal/117998313/abstract#fn1> ‡, Rona

Limor*, Etty Osher*, Sabina Lewicka†, Vecsei† and Naftali Stern*

*Institute of Endocrinology, Metabolism and Hypertension, Tel Aviv –

Sourasky Medical Center, Tel Aviv University, Tel Aviv, Israel ,

†Institute of Pharmacology, Ruprecht-Karls-University, Heidelberg, Germany

Correspondence: Naftali Stern, Institute of Endocrinology, Tel Aviv –

Sourasky Medical Center, 6 Weizmann St. Tel Aviv 64239, Israel. Tel: +972

36973732; Fax: +972 36974578; E-mail: <mailto:> stern@...

Copyright © 2007 The Authors

Journal compilation © 2007 Blackwell Publishing Ltd

Summary

Background The rapid re-accumulation of fluid following aspiration of

thyroid cystic lesions suggests that active transport of sodium and water

may be involved in volume regulation of these lesions. In this study we

address the possibility that aldosterone may take part in this process.

Subjects and methods Thirty-one patients (29 women and two men), with a mean

age of 52·7 ± 13·2 years (range: 27–77 years) underwent evaluation for

thyroid nodules that had a sonographic cystic component. Cystic fluid

obtained by FNA biopsy was sent for cytological examination and biochemical

measurements. In 10 patients, material was collected for RNA extraction and

determination of aldosterone synthase expression by RT-PCR amplification.

Results All lesions were benign, cystic, colloid nodules. Cyst fluid

aldosterone levels as measured by routine radioimmunoassay (RIA) were

elevated above the normal plasma levels in all but five patients. Mean

aldosterone levels were 27·1 ± 22·9 ng/dl (SD) (range: 5·9–117·5 ng/dl). In

contrast, cyst cortisol values were in the low, low normal serum range (6·2

± 2·9 µg/dl, range: 0·2–10·2 µg/dl). Sodium, chloride and potassium levels

were 137 ± 4·7 mEq/l, 98 ± 5 mEq/l and 4·9 ± 1·4 mEq/l, respectively. Plasma

aldosterone levels were normal in all patients tested. To confirm these

results, 12 samples were assayed after extraction and chromatography using a

highly specific antibody. Cyst aldosterone levels in this group were

elevated above the normal serum range in all but one patient (mean

concentration: 24·5 ± 14·6 ng/dl, range: 8·72–40·1 ng/dl). In this group,

18(OH)B levels were within the normal plasma range (12–55 ng/dl) in all but

one patient (34·9 ± 17 ng/dl). Furthermore, aldosterone synthase mRNA

expression was found in aspirates of four of 10 patients.

Conclusions The increased aldosterone concentration and the presence of

aldosterone synthase expression suggest that aldosterone may be locally

produced and secreted in thyroid tissue. The pathophysiological implications

of this finding remain to be established.

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(Received 13 September 2006; returned for revision 27 October 2006; finally

revised 25 December 2006; accepted 4 January 2007)