Endocrine Abstracts

Case: A 63-year-old acromegalic woman admitted hospital for lassitude and dizziness. She has been diagnosed acromegaly 10 years ago and had two transsphenoidal operations. Remission wasn’t achieved. Then she started to use lanreotide (somatostatin analogue) and for 7 years she has been treated with it. In laboratory examination, basal plasma GH 1.21 ng/ml (NR:0–5); nadir GH level after glucose tolerance test, 1.2 ng/ml (NR: less than 1); IGF1, 129.1 ng/ml (NR: for age: 75–212); thyroid stimulating hormone (TSH), 0.824 uIU/ml (NR: 0.27–4.2); free thyroxine (fT₄), 1.26 ng/dl (NR: 0.9–1.7); and prolactin, 6.66 ng/ml (NR in women: 0–20). MRI with gadolinium contrast revealed a pituitary microadenoma. Routine resting electrocardiograms of patient showed bradycardia (46 bpm) and supraventicular extrasystoles. Then lanreotide treatment stopped. Patient’s symptoms relieved and heart rate increased (64 bpm).

Conclusion: Somatostatin is a peptide hormone with a short half-life (2–3 min), which is synthesized in multiple tissues, including the hypothalamus, to inhibit GH secretion. Somatostatin analogues (octreotide and lanreotide) are indicated principally for the treatment of acromegaly that remains active after transsphenoidal surgery, whether or not the patient has also undergone radiotherapy. Octreotide-induced bradycardia has previously been reported as an unusual finding in different clinical situations (nonacromegalic patients) and a male patient with acromegaly. A rat study shows bilateral microinjection into the rostral ventrolateral medulla of either somatostatin or the receptor-selective agonist lanreotide evoked dramatic, dose-dependent sympathoinhibition, hypotension, and bradycardia. Our case is the first reported patient with acromegaly who had bradycardia and supraventricular extrasystoles associated with use of lanreotide.