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Inmyung Yang, Jeongtaek Woo, Sungwoon Kim, Jinwoo Kim, Youngseol Kim and Youngkil Choi

Yang I, Woo J, Kim S, Kim J, Kim Y, Choi Y. Combined pyridostigmine–thyrotrophin-releasing hormone test for the evaluation of hypothalamic somatostatinergic activity in healthy normal men. Eur J Endocrinol 1995;133:457–62. ISSN 0804–4643

Pyridostigmine (PST), a cholinesterase inhibitor, induces a clear growth hormone (GH) release in man by suppression of hypothalamic somatostatin (SRIH). Somatostatin suppresses thyrotrophin (TSH) release in rats and men. Earlier studies showed that the thryotrophin-releasing hormone (TRH)-induced TSH response was not altered by 60–120 mg of PST. We studied whether a larger dose (180 mg) of PST can increase the TSH response to TRH. Six healthy young men were studied with the following six tests: (Test 1) 200 μg of TRH iv; (Test 2) 180 mg of PST po; (Test 3) three different doses of PST (60, 120, 180 mg) + TRH; (Test 4) 100 μg of octreotide (SMS) iv; (Test 5) SMS + TRH; (Test 6) PST + SMS + TRH. A large dose of PST (180 mg) significantly augmented GH, TSH and prolactin responses to TRH, while smaller doses of PST (60 and 120 mg) did not significantly increase the responses of GH and TSH. While the increased TRH-induced prolactin response by PST was not suppressed by SMS, the increased responses of GH and TSH were suppressed remarkably by SMS. Most of the subjects noticed a mild to moderate abdominal pain, nausea and muscular fasciculation after the administration of a large dose of PST administration. These data suggest that suppression of hypothalamic SRIH secretion by 180 mg of PST can augment the TSH response to TRH. However, the considerable side effects should be minimized before clinical application of the combined PST–TRH test.

Inmyung Yang, Division of Endocrinology, Department of Internal Medicine, Kyunghee University School of Medicine, 1 Hoiki-dong, Dongdaemoon-ku, Seoul, 130–702, Korea

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Inmyung Yang, Seungjoon Park, Meesook Ryu, Jeongtaek Woo, Sungwoon Kim, Jinwoo Kim, Youngseol Kim and Youngkil Choi

Yang I, Park S, Ryu M, Woo J, Kim S, Kim J, Kim Y, Choi Y. Characteristics of gsp-positive growth hormone-secreting pituitary tumors in Korean acromegalic patients. Eur J Endocrinol 1996;134: 720–6. ISSN 0804–4643

A subset of human growth hormone (GH)-secreting pituitary tumors contains the gsp oncogene that encodes an activation mutation of the α-subunit of the stimulatory GTP-binding protein (Gsα). This study was undertaken to investigate the frequency of the gsp oncogene in GH-secreting pituitary tumors in Korean acromegalic patients and to elucidate the clinical characteristics of these patients to endocrine testing. Direct polymerase chain reaction sequencing revealed the gsp oncogene mutation in 9 out of 21 tumors (43%) at amino acid 201 of the Gsα protein. A single nucleotide mutation in the tumors carrying the gsp oncogene was observed, which replaced an arginine (CGT) in the normal protein with cysteine (TGT) in eight tumors and serine (AGT) in one tumor. The patients with the gsp oncogene mutation (group 1) were older (54 ± 10 vs 41 ±11 years, p = 0.0085) than those without the mutation (group 2). Sex, tumor size and grade, basal GH and prolactin levels, the GH response to oral glucose loading, the GH fluctuation and the paradoxical response to thyrotropin-releasing hormone or gonadotropin-releasing hormone did not differ between the groups. The gsp oncogene was found mostly in somatotroph adenomas. The octreotide-induced GH suppression was significantly higher in group 1 than in group 2 (95 ± 5% vs 81 ± 17%, p = 0.0335). The GH response to bromocriptine did not differ between the groups. These results suggest that the Gsα mutations of GH-secreting tumor are observed in Korean acromegalic patients with similar frequency to those of western countries. The patients with gsp oncogene are likely to be older than those without the oncogene, and show excellent response of GH suppression to octreotide.

Inmyung Yang, Division of Endocrinology, Department of Internal Medicine, Kyunghee University School of Medicine, 1 Hoiki-dong, Dongdaemoon-ku, Seoul 130-702, Korea