Treatment of acromegaly with oral octreotide

Acromegaly is a rare chronic disease caused in most cases by a growth hormone (GH) secreting pituitary adenoma. The estimated prevalence of the disease varies from 2.8 to 13.7 cases per 100,000 people [1], [2]. GH and consequently insulin-like growth factor-1 (IGF-1) excess are responsible for cardiovascular, metabolic, and musculoskeletal comorbidities that lead to increased morbidity and mortality in patients with acromegaly [3], [4]. GH is normally secreted by somatotropic cells in the anterior pituitary gland and is closely regulated by stimulatory hormones such as growth hormone releasing hormone and ghrelin, and inhibited by somatostatin [5]. In acromegaly, tumoral GH secretion and GH-induced hepatic secretion of IGF-1 are also inhibited by somatostatin through the activation of G protein-coupled receptors (SSTR1-SSTR5) [6], [7]. The normal pituitary gland expresses high concentrations of SSTR5 and SSTR2 and lower concentrations of SSTR 3 and SSTR1, and many pituitary adenomas express SSTR5, SSTR2 and SSTR3 [8], [9]. Somatotroph adenomas predominantly express SSTR2 and SSTR5 [10], rendering therapy with somatostatin receptor ligands (SRL) highly effective for suppressing GH hypersecretion and decreasing tumoral mass [11], [12]. Biochemical control of IGF-1 and GH in acromegaly is associated with a reduction of mortality and morbidity as well as improved quality of life [13], [14]. SRLs are the treatment of choice in patients with acromegaly who have significant elevations of IGF-1 and/or concern for tumour remnants after surgery, or who refuse or are not candidates for surgery [3]. The most commonly used formulations of these therapies include injectable SRLs such as octreotide long-acting release (LAR), lanreotide depot and pasireotide LAR. However, oral octreotide presents a novel alternative for patients who prefer oral therapies over monthly injections. This article reviews the current literature on oral octreotide including its mechanism of action, its therapeutic indications, and its role in clinical practice.

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