J Korean Med Sci.  2013 Dec;28(12):1774-1780. 10.3346/jkms.2013.28.12.1774.

Change in Somatostatinergic Tone of Acromegalic Patients according to the Size of Growth Hormone-Producing Pituitary Tumors

• Chin SO
• Chon S
• Hwang YC
• Jeong IK
• Oh S
• Kim SW

• KMID: 1779419
• DOI: http://doi.org/10.3346/jkms.2013.28.12.1774

Abstract

The aim of this study was to investigate the relationship between somatostatinergic tone (SST) and the size of growth hormone (GH)-producing pituitary tumors. GH levels of 29 patients with newly diagnosed acromegaly were measured using a 75-gram oral glucose tolerance test (OGTT), an insulin tolerance test (ITT), and an octreotide suppression test (OST). Differences between GH levels during the ITT and the OGTT (DeltaGH(IO)), and between the OGTT and the OST at the same time point (DeltaGH(OS)) were compared according to the size of the tumor and the response pattern to the OST. DeltaGH(IO) of macroadenomas (n=22) was non-significantly higher than those of microadenomas while DeltaGH(OS) of macroadenomas were significantly higher than those of microadenomas. According to further analyses of macroadenomas based on the response pattern to the OST, GH levels during the ITT were significantly higher in non-responders. DeltaGH(OS) showed near-significant differences between responders and non-responders. In conclusion, as the size of the pituitary tumor increases, the effect of glucose on SST appears to be attenuated. Macroadenomas that are non-responders to the OST possess a portion of GH secretion exceeding the range of regulation by SST.

Keyword

Acromegaly; Growth Hormone; Somatostatinergic Tone; Pituitary Gland; Macroadenomas

MeSH Terms

Acromegaly/*diagnosis/*pathology
Adenoma/drug therapy/*pathology
Adult
Aged
Antineoplastic Agents, Hormonal/therapeutic use
Female
Glucose Tolerance Test
Human Growth Hormone/*blood/secretion
Humans
Insulin/blood
Insulin-Like Growth Factor I/analysis
Male
Middle Aged
Octreotide/therapeutic use
Pituitary Neoplasms/drug therapy/*pathology
Antineoplastic Agents, Hormonal
Human Growth Hormone
Insulin
Insulin-Like Growth Factor I
Octreotide

Figure

• 

  Fig. 1 Comparison of GH levels between macroadenomas and microadenomas during (A) the ITT (B) the OGTT (C) the OST: Data represent mean±standard error. LMM was used for the statistical comparison. GH, growth hormone; ITT, insulin tolerance test OGTT, oral glucose tolerance test; OST, octreotide suppression test; LMM, linear mixed model.

• 

  Fig. 2 Change in difference of GH levels (A) between the ITT and the OGTT (ΔGHIO); (B) between the OGTT and the OST (ΔGHOS) in macroadenomas and microadenomas. Data represent mean±standard error. LMM was used for the statistical comparison. GH, growth hormone; ITT, insulin tolerance test; OGTT, oral glucose tolerance test; OST, octreotide suppression test; Macro, macroadenomas; micro, microadenomas; LMM, linear mixed model.

• 

  Fig. 3 Comparison of GH levels between responders and non-responders of macroadenomas during (A) the ITT (B) the ITT (C) the OST. Data represent mean±standard error. LMM was used for the statistical comparison. GH, growth hormone; ITT, insulin tolerance test OGTT, oral glucose tolerance test; OST, octreotide suppression test; LMM, linear mixed model.

• 

  Fig. 4 Change in difference of GH levels (A) between the ITT and the OGTT (ΔGHIO); (B) between the OST and the OGTT (ΔGHOS) in responders and non-responders of macroadenomas. Data represent mean±standard error. LMM was used for the statistical comparison. GH, growth hormone; ITT, insulin tolerance test; OGTT, oral glucose tolerance test; OST, octreotide suppression test; LMM, linear mixed model.

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