Acromegaly in a domestic short-haired cat: first report from Iran.

Abstract

Acromegaly, a syndrome characterized by overgrowth of bony and soft tissue, is caused following chronic excessive production of growth hormone (GH)[1]. It is a well-recognized but rare condition in cats caused by a functional somatotroph adenoma in the anterior pituitary gland[2,3]. This disorder is encountered most often in middle-aged and elderly, predominantly male, cats[1]. Catabolic and diabetogenic effects of GH, the anabolic effects of IGF-1 and the space-occupying effect of the pituitary adenoma are responsible for clinical signs[4]. The physical changes in cats tend to be less pronounced than in dogs. Increased body size, especially large head and abdominal enlargement are prominent. Affected cats may have respiratory signs, which is due to soft tissue thickening in the pharyngeal region and consequent extrathoracic upper airway obstruction. Moreover, hypertrophic cardiomyopathy is another cause of dyspnea in these cases. Neurological signs resulting from large pituitary adenoma may also manifest[3,5]. In advanced cases, clinical manifestation may include prominent facial features, generalized bone/soft tissue enlargement, and prognathia[5]. An association between pituitary adenoma and diabetes mellitus (DM) was well described in cats[6]. More recently, feline acromegaly has been reported in several cats with concurrent insulin-resistant DM[7,8]. A GH-induced postreceptor defect in insulin action at the level of target tissues is believed to be the cause of concurrent diabetes in most cats with acromegaly[2]. Acromegaly is mainly diagnosed based upon increased serum GH concentration[9]. Computed tomography (CT) or magnetic resonance (MR) imaging of the head is also recommended to confirm the presence of a pituitary tumor[10]. Radiation therapy has been reported as the most effective treatment for feline acromegaly. It leads to improved neurologic signs and decreased insulin requirements[3,5]. This study is the first case report of a diabetic cat with acromegaly in Iran, which described historic and clinical signs and laboratory findings associated with the condition.