Poor responses to a test dose of subcutaneous octreotide predict the need for adjuvant therapy to achieve 'safe' growth hormone levels.
OBJECTIVE
Somatostatin analogues are an established treatment in acromegaly. This study was designed to evaluate whether the acute serum growth hormone (GH) response to a test dose of octreotide in acromegaly predicts longer-term response to the drug at 3 years.


METHODS
In 23 patients, GH responses across 8 h to a subcutaneous test dose (50 microg) of octreotide were compared with GH levels after 3 years of therapy. The majority had pituitary surgery as primary therapy and at 3 years were receiving at least 600 microg octreotide daily subcutaneously or 20 mg LAR monthly intramuscularly.


RESULTS
Seven had a test day GH Nadir of 5 mU/l or less of whom 4 achieved GH < 5 mU/l at 3 years. Sixteen had a test day nadir GH of 10 mU/l or less and of these 8 achieved GH < 5 mU/l at 3 years. Seven of the 23 had a GH Nadir >10 mU/l and of these 3 had achieved GH <5 mU/l at 3 years. However all of these 3 had received external pituitary irradiation within 4 years of the 3 year assessment, as compared with 3 of the <5 mU/l nadir group and 5 of the <10 mU/l nadir group.


CONCLUSIONS
In patients on optimal long-term doses of octreotide for acromegaly, absence of a nadir GH <10 mU/l in the 8 h after a test dose was associated with failure to achieve GH levels associated with a normal life expectancy (5 mU/l or less) unless adjunctive external pituitary irradiation was given. As well as testing tolerability a test dose of octreotide may help in determining which patients should be offered early external pituitary irradiation or therapy with a GH receptor antagonist if surgery has failed to achieve 'safe' GH levels.
Lindsay
J R
JR
Regional Centre for Endocrinology and Diabetes, Royal Victoria Hospital, Grosvenor Rd, Belfast, UK.
McConnell
E M
EM
Regional Centre for Endocrinology and Diabetes, Royal Victoria Hospital, Grosvenor Rd, Belfast, UK.
Hunter
S J
SJ
Regional Centre for Endocrinology and Diabetes, Royal Victoria Hospital, Grosvenor Rd, Belfast, UK.
McCance
D R
DR
Regional Centre for Endocrinology and Diabetes, Royal Victoria Hospital, Grosvenor Rd, Belfast, UK.
Sheridan
B
B
Regional Endocrine Laboratory, Royal Victoria Hospital, Grosvenor Rd, Belfast, UK.
Atkinson
A B
AB
Regional Centre for Endocrinology and Diabetes, Royal Victoria Hospital, Grosvenor Rd, Belfast, UK. ab.atkinson@royalhospitals.n-i.nhs.uk.|Regional Centre for Endocrinology and Diabetes, Royal Victoria Hospital, Grosvenor Rd, Belfast, BT12 6BA, UK. ab.atkinson@royalhospitals.n-i.nhs.uk.
D000172:Acromegaly / Q000097:blood / Q000188:drug therapy* / Q000532:radiotherapy / Q000601:surgery; D000293:Adolescent; D000328:Adult; D000368:Aged; D003131:Combined Modality Therapy; D004305:Dose-Response Relationship, Drug; D005260:Female; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D007273:Injections, Intramuscular; D007279:Injections, Subcutaneous; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D008297:Male; D008875:Middle Aged; D015282:Octreotide / Q000008:administration & dosage* / Q000627:therapeutic use*; D010902:Pituitary Gland / Q000187:drug effects / Q000528:radiation effects / Q000601:surgery; D013997:Time Factors
D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D015282:Octreotide