Pruritus in acromegaly: Coexistence of Graves' disease

Background Disorders in thyroid function and goiter can be seen in acromegaly patients due to prolonged stimulation of follicular epithelium by growth hormone (GH) and insulin-like growth factor (IGF-1). The coexistence of acromegaly and Graves' disease is very unusual, the prevalence being <1%. Case Presentation 70-year-old man with macroadenoma which was secreting both growth hormone and prolactin was followed in endocrine clinic. He had previously declined intervention. On physical exam, he had gross facial features such as macroglossia, prognathia, increased soft tissue around the face, neuropathy and carpal tunnel of both hands, thyromegaly in the past (biopsy- mild atypia), subclinical hyperthyroidism ( Graves' disease ) and type 2 diabetes mellitus. During the hospital admission for hyperglycemia, he developed severe headache. MRI suggested enlargement of the pituitary tumor. He was then transferred to neurosurgery and had resection of tumor. Pathology report showed pituitary apoplexy with infarcted glandular tissue and viable portions of neurohypophysis. He went home on only hydrocortisone 20 mg in am and 10 mg in pm. Hydrocortisone was tapered off without problems. Vision has gotten better after surgery. After surgery, he developed generalized burning sensation, hot flushes and sweats. Steroid injection courses, stopping gabapentin and insulin did not help. Testosterone was started every 2 weeks and the symptoms were better but still present. Thyroid function testing revealed free T4 was higher than in the past, and TSH was completely suppressed. Trial of methimazole was started. Discussion Thyroid cell proliferation and differentiation is regulated by thyrotropin and Graves' IgGs and the tyrosine kinase IGF1 receptor by activating the G protein-coupled receptor TSH receptor. These autoantibodies activate distinct G proteins and signaling pathways in follicular cells of the thyroid gland. Acromegaly can coexist with hyperthyroidism due to Graves' disease. If a patient with acromegaly gets the symptoms of hyperthyroidism such as palpitation or weight loss, Graves' disease should be considered. Our patient had asymptomatic subclinical Graves' disease which progressed to symptomatic state. According to Di Cerb. A et al, severity of Graves' disease is exacerbated by coexistent acromegaly and Graves' disease improves after the surgical remission of acromegaly. Pruritus is an uncommon presentation of hyperthyroidism and the pathophysiology is still unclear. Schocket AL. stated that pruritus in autoimmune thyroid disorders is a manifestation of cell-mediated immunity, which lowers the mast cell threshold for the release of histamine. Conclusion Coexisting Graves' disease should be considered in acromegaly patients presenting with pruritus. Our report will benefit the clinicians in their differential diagnoses development and management.