Expression of 5'-deiodinase enzymes in normal pituitaries and in various human pituitary adenomas.
OBJECTIVE
Local 5'-deiodination of l-thyroxine (T(4)) to active thyroid hormone 3,3',5-tri-iodothyronine (T(3)) catalyzed by the two 5'-deiodinase enzymes (D1 and D2) regulates various T(3)-dependent functions in the anterior pituitary and has been well studied in rodents. Only limited information about deiodinase expression and its cellular distribution in human anterior pituitaries is available.


METHODS
We examined 5'-deiodinase enzyme activities in pituitary adenomas (18 non-functioning, seven TSH-producing, one GH- and TSH-producing, five GH-producing, eight prolactin (PRL)-producing, two adenomas each from patients with Cushing's disease and Nelson's syndrome) and three normal anterior pituitaries.


METHODS
Activities were measured as release of (125)I(-) from tyrosyl-ring labeled reverse T(3) with or without propylthiouracil, a potent inhibitor of D1 which does not influence D2 activities.


RESULTS
Most of the adenomas and normal tissues expressed both isoenzymes, with D2 activity higher than D1. In a few tissues D1 activity was higher than D2 and some tissues did not express D1 activity at all. Highest activities of both enzymes were found in TSH- and PRL-producing adenomas but absolute activities and the D1/D2 ratio were variable in the same kind of tumor in different patients.


CONCLUSIONS
The finding that all examined tissues expressed 5'-deiodinase activity, most of them expressing both isoenzymes, implies that both enzymes are still active in tumors and that local deiodination is important for the function and feedback regulation of human anterior pituitary.
Baur
A
A
Abteilung für Molekulare Innere Medizin und Klinische Forschergruppe der Medizinischen Poliklinik der Universität Würzburg, Germany.
Buchfelder
M
M
Köhrle
J
J
D000236:Adenoma / Q000201:enzymology* / Q000378:metabolism; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D003480:Cushing Syndrome / Q000201:enzymology; D005260:Female; D019382:Human Growth Hormone / Q000096:biosynthesis; D006801:Humans; D007453:Iodide Peroxidase / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009347:Nelson Syndrome / Q000201:enzymology; D010902:Pituitary Gland / Q000201:enzymology*; D010903:Pituitary Gland, Anterior / Q000201:enzymology; D010911:Pituitary Neoplasms / Q000201:enzymology* / Q000378:metabolism; D011388:Prolactin / Q000096:biosynthesis; D013972:Thyrotropin / Q000096:biosynthesis; D000097564:Iodothyronine Deiodinase Type II
D019382:Human Growth Hormone; D007453:Iodide Peroxidase; D007527:Isoenzymes; D011388:Prolactin; D013972:Thyrotropin; D000097564:Iodothyronine Deiodinase Type II; C109812:iodothyronine deiodinase type I