The hypothalamus-pituitary function after pituitary stereotactic radiosurgery: evaluation of growth hormone deficiency.
OBJECTIVE
Radiation therapy to the pituitary gland means a considerable risk of developing hypopituitarism. The aim of the study was to investigate the growth hormone releasing hormone (GHRH)-growth hormone (GH)-insulin-like growth factor-I (IGF-I) axis after treatment with stereotactic radiosurgery to the pituitary because of Cushing's disease.


METHODS
Inpatient ward in university clinic.


METHODS
Eleven adult patients (eight women, three men), 20-65 years of age were studied 2.5-11.3 years after stereotactic radiosurgery (isocentre dose 50-100 Gy lesion-1) and compared with healthy controls.


METHODS
Spontaneous GH secretion was evaluated as 12-h night GH profiles. Stimulated GH responses were evaluated in seven of 11 patients using arginine-insulin and GHRH tests. Serum IGF-I levels were measured in fasting serum morning samples.


RESULTS
All patients except one displayed blunted nocturnal GH profiles. After arginine-insulin challenge, six of seven patients displayed low GH release. GH response was higher after GHRH injection compared with both the response to arginine-insulin and to the maximum GH levels in the nocturnal profiles. Seven patients had an IGF-I standard deviation score (SDS) within the normal range for age. Serum IGF-I values were correlated to mean GH values in the 12-h night profile (r = 0.67, P < 0.05) and both these variables were negatively correlated to time elapse since last radiation treatment (r = -0.64, P < 0.05 and r = -0.78, P < 0.05, respectively).


CONCLUSIONS
Our patients with Cushing's disease evaluated several years after stereotactic radiosurgery as the primary and only treatment, demonstrated severely blunted spontaneous GH secretion and GH response to arginine-insulin. A disturbed regulation at the hypothalamic level was suggested as mechanism for this. Noteworthy is that serum IGF-I values correlated to the mean values of the 12-h GH profile.
Degerblad
M
M
Department of Endocrinology and Diabetology, Karolinska Hospital, Stockholm, Sweden. Marie.Degerblad@molmed.ki.se
Brismar
K
K
Rähn
T
T
Thorén
M
M
D000328:Adult; D000368:Aged; D001120:Arginine; D003480:Cushing Syndrome / Q000378:metabolism / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D013007:Growth Hormone-Releasing Hormone / Q000378:metabolism; D019382:Human Growth Hormone / Q000172:deficiency* / Q000378:metabolism; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology / Q000528:radiation effects*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010902:Pituitary Gland / Q000378:metabolism / Q000528:radiation effects*; D016634:Radiosurgery / Q000009:adverse effects*
D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D013007:Growth Hormone-Releasing Hormone; D001120:Arginine