Growth hormone (GH) secretory dynamics in a case of acromegalic gigantism associated with hyperprolactinemia: nonpulsatile secretion of GH may induce elevated insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 levels.
We describe a case of pituitary gigantism with low levels of growth hormone (GH), elevated insulin-like growth factor-I (IGF-I), and IGF-binding protein-3 (IGF-BP-3). The patient had characteristic clinical features of gigantism and acromegaly. The basal serum GH levels ranged from 1.2-1.9 micrograms/L, which were considered to be within normal limits. Serum GH response to either insulin-induced hypoglycemia or GH-releasing hormone was blunted. Frequent blood samplings during daytime and at night showed nonpulsatile GH secretion. Serum prolactin, IGF-I and IGF-binding protein-3 levels were elevated. After unsuccessful surgery, bromocryptine treatment normalized serum prolactin without affecting serum GH and IGF-I levels. Combined administration of octreotide and bromocryptine reduced serum GH and IGF-I levels. GH bioactivity as measured by Nb2 cell proliferation assay was within reference range. In the present case, nonpulsatile GH secretion and enhanced tissue sensitivity to GH may induce hypersecretion of IGF-I and IGF-BP-3 and cause clinical acromegalic gigantism.
First Department of Internal Medicine, Kyoto Prefectural University of Medicine, Japan.
T
T
Yoshida
A
A
Shimatsu
N
N
Sakane
N
N
Hizuka
R
R
Horikawa
T
T
Tanaka
D000172:Acromegaly / Q000378:metabolism*; D000328:Adult; D005877:Gigantism / Q000378:metabolism*; D013006:Growth Hormone / Q000378:metabolism*; D006801:Humans; D006966:Hyperprolactinemia / Q000378:metabolism*; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008297:Male; D011388:Prolactin / Q000378:metabolism
D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I; D011388:Prolactin; D013006:Growth Hormone