Effects of therapy with [177Lu-DOTA0,Tyr 3]octreotate on endocrine function

Purpose: Peptide receptor radionuclide therapy (PRRT) with radiolabelled somatostatin analogues is a novel therapy for patients with somatostatin receptor-positive tumours. We determined the effects of PRRT with [177Lu-DOTA0,Tyr3]octreotate (177Lu-octreotate) on glucose homeostasis and the pituitary-gonadal, pituitary-thyroid and pituitary-adrenal axes. Methods: Hormone levels were measured and adrenal function assessed at baseline and up to 24 months of follow-up. Results: In 35 men, mean serum inhibin B levels were decreased at 3 months post-therapy (205 ± 16 to 25 ± 4 ng/l, p < 0.05) and follicle-stimulating hormone (FSH) levels increased (5.9 ± 0.5 to 22.7 ± 1.4 IU/l, p < 0.05). These levels returned to near baseline levels. Total testosterone and sex hormone binding globulin (SHBG) levels decreased (15.0 ± 0.9 to 10.6 ± 1.0 nmol/l, p < 0.05 and 61.8 ± 8.7 to 33.2 ± 3.7 nmol, p < 0.05), respectively, whereas non-SHBG-bound T did not change. An increase (5.2 ± 0.6 to 7.7 ± 0.7 IU/l, p < 0.05) of luteinizing hormone (LH) levels was found at 3 months of follow-up returning to baseline levels thereafter. In 21 postmenopausal women, a decrease in levels of FSH (74.4 ± 5.6 to 62.4 ± 7.7 IU/l, p < 0.05) and LH (26.8 ± 2.1 to 21.1 ± 3.0 IU/l, p < 0.05) was found. Of 66 patients, 2 developed persistent primary hypothyroidism. Free thyroxine (FT4) levels decreased (17.7 ± 0.4 to 15.6 ± 0.6 pmol/l, p < 0.05), whereas thyroid-stimulating hormone (TSH) and triiodothyronine (T3) levels did not change. Reverse triiodothyronine (rT3) levels decreased (0.38 ± 0.03 to 0.30 ± 0.01 nmol/l, p < 0.05). Before and after therapy adrenocorticotropic hormone (ACTH) stimulation tests showed an adequate response of serum cortisol (> 550 nmol/l, n = 18). Five patients developed elevated HbA1clevels (> 6.5%). Conclusion: In men177Lu-octreotate therapy induced transient inhibitory effects on spermatogenesis, but non-SHBG-bound T levels remained unaffected. In the long term, gonadotropin levels decreased significantly in postmenopausal women. Only a few patients developed hypothyroidism or elevated levels of HbA1c. Therefore, PRRT with177Lu-octreotate can be regarded as a safe treatment modality with respect to short-and long-term endocrine function.