Abstract and Introduction
Abstract
Objective: To describe a case of muscle weakness in a patient with acromegaly and to review the pathophysiologic features of this disorder.
Methods: We present the clinical, laboratory, electromyographic, and muscle biopsy findings in our patient and review related reports in the literature.
Results: A 58-year-old woman with acromegaly presented with complaints of bilateral hip pain, weakness, and instability 8 months after transsphenoidal resection of a growth hormone (GH)-secreting pituitary macroadenoma. She had biochemically normal thyroid and adrenal function and no evidence of any neuropathy, inflammatory myopathy, or rheumatologic disorder to explain her symptoms. Investigations revealed increased levels of GH, insulin-like growth factor-I, serum creatine kinase (CK), and the MB fraction of CK, normal results of nerve conduction studies, and nonspecific findings on electromyography and muscle biopsy. A review of the literature revealed that although muscle weakness is a well-recognized feature of acromegaly, only a few cases similar to ours have been reported since acromegaly was first described in the late 1800s. Little is known about the natural history, best diagnostic approach, and optimal therapy for this debilitating complication.
Conclusion: Muscle weakness in acromegaly is common and may result from a combination of the direct effect of GH excess on muscle and other metabolic derangements (hypothyroidism, hypoadrenalism, or diabetes). Mechanical factors may also contribute, such as joint laxity in conjunction with hypermobility. Affected patients may benefit from a reduction in GH levels and physiotherapy for adaptive training. Persistently increased serum CK levels in a patient with diabetes, for whom no other cause is found, should prompt an investigation for acromegaly. More research into this aspect of acromegaly is needed for enhancement of our understanding of, and therapy for, this debilitating condition.
Introduction
The short-term effects of systemic excess of growth hormone (GH) include stimulation of synthesis of muscle protein without an increased synthesis of whole-body protein; this finding suggests a specific targeted effect of GH on muscle metabolism.[1,2] In addition, long-term GH replacement in adults with GH deficiency has been shown to improve muscle size, strength, and exercise tolerance.[3-6] Unlike short-term studies, prolonged exposure to excess GH seems to have detrimental effects on muscle strength. We present the case of a 58-year-old woman with acromegaly who had features of myopathy approximately 7 years after the onset of symptoms of acromegaly, and we review the literature regarding acromegalic myopathy and possible factors contributing to muscle weakness in patients with acromegaly.
