From Lewis S Blevins, Jr. MD – I recently addressed a question regarding normal oral glucose suppression test results in a patient who reportedly looked as if they had acromegaly. I wanted to share my clinical reasoning with the group.
Firstly, some patients with small pituitary adenoma’s producing growth hormone will actually suppress growth hormone levels with oral glucose. Thus, it is necessary to obtain an IGF-I level to complete the evaluation. If the IGF-I level is elevated then an MRI would be performed to evaluate for the possibility of a pituitary adenoma. If the scan were negative then a GHRH level should be performed to entertain the possibility of a GHRH–secreting neuroendocrine tumor located elsewhere.
If the IGF-I level proves to be normal in a patient who has definite clinical features of acromegaly then there are several possibilities. Firstly, some patients with acromegaly have tumors that hemorrhage and auto infarct then undergo necrosis. There growth hormone and IGF-I levels will fall to normal and sometimes a develop growth hormone deficiency. Some have varying degrees of hypopituitarism. Many of these patients have a partial or nearly empty sella, expansion of the sella turcica, and an irregular pituitary gland. Thus, MRI can be useful to provide insight into the fact that an acromegaloid patient with normal biochemistry may have once had a pituitary tumor. Next, there is a disorder called acromegaloidism where patient’s may have thickened furrows on the skin of the scalp (cutis gyrata vertica), enlarged brows, and prognathism. Of course, some patients have familial prognathism that is unrelated to growth hormone secretion. Lastly, the syndrome of insulin resistance can produce an acromegaloid appearance.
Most of the time, regardless of the disease process, we try to triangulate or base a diagnosis on symptoms, signs, and diagnostic tests (laboratory and radiologic exams). Acromegaly is certainly no exception. It serves as a classic example of a disorder where one has to know not only about the disease process itself but also about the great imitators that are, in some cases, more common than the disease in question.
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