In vivo and in vitro response to octreotide LAR in a TSH-secreting adenoma: characterization of somatostatin receptor expression and role of subtype 5

Thyrotropin-secreting pituitary adenomas (TSHomas) are a rare cause of hyperthyroidism and account for less than 2% of pituitary adenomas. Medical therapy with somatostatin analogues (SSAs) effectively reduces TSH secretion in approximately 80% of patients and induces shrinkage in about 45% of tumor...

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Bibliographic Details
Published in:Pituitary 2011-06, Vol.14 (2), p.141-147
Main Authors: Gatto, Federico, Barbieri, Federica, Castelletti, Lara, Arvigo, Marica, Pattarozzi, Alessandra, Annunziata, Francesca, Saveanu, Alexandru, Minuto, Francesco, Castellan, Lucio, Zona, Gianluigi, Florio, Tullio, Ferone, Diego
Format: Article
Language:English
Subjects:
Adenoma - drug therapy
Adenoma - genetics
Adenoma - secretion
Adult
Antineoplastic Agents, Hormonal - administration & dosage
Antineoplastic Agents, Hormonal - pharmacology
Cells, Cultured
Delayed-Action Preparations - administration & dosage
Delayed-Action Preparations - pharmacology
Endocrinology
Gene Expression Regulation, Neoplastic - drug effects
Human Physiology
Humans
Male
Medicine
Medicine & Public Health
Octreotide - administration & dosage
Octreotide - pharmacology
Pituitary Neoplasms - drug therapy
Pituitary Neoplasms - genetics
Pituitary Neoplasms - secretion
Receptors, Somatostatin - genetics
Receptors, Somatostatin - metabolism
Receptors, Somatostatin - physiology
Thyrotrophs - metabolism
Thyrotrophs - pathology
Thyrotropin - secretion
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Summary:Thyrotropin-secreting pituitary adenomas (TSHomas) are a rare cause of hyperthyroidism and account for less than 2% of pituitary adenomas. Medical therapy with somatostatin analogues (SSAs) effectively reduces TSH secretion in approximately 80% of patients and induces shrinkage in about 45% of tumors. According with previous data, resistance to SSA treatment might be due to heterogeneity in somatostatin receptors (SSTRs) expression. We report the case of TSHoma in a 41-year-old man treated with octreotide LAR that caused a dramatic decrease of TSH and thyroid hormones and tumor shrinkage already after 3 months of pre-surgical therapy. In search of potential molecular determinants of octreotide effectiveness, we measured, in primary cultures from this tumor, SSTR and dopamine D2 receptor (D2R) expression, and octreotide and/or cabergoline effects on TSH secretion and cell proliferation. SSTR5 and D2R expression was higher than SSTR2. Octreotide significantly inhibited TSH secretion more effectively than cabergoline ( P  
ISSN:1386-341X
1573-7403
DOI:10.1007/s11102-010-0271-2