1/6. "Hook effect" in prolactinomas: case report and review of literature.OBJECTIVE: To present a case of the "hook effect" occurring in the prolactin immunoassay in a patient with giant prolactinoma and to review this phenomenon. methods: We describe the clinical, biochemical, radiologic, and pathologic data of a patient with a giant prolactinoma, in which dilution testing of serum prolactin levels confirmed the presence of the hook effect. We discuss the historical and mechanistic aspects of the hook effect and then review its occurrence with the prolactin assay. RESULTS: A 65-year-old man sought medical attention because of headaches, personality changes, and "bulging" eyes. Cranial magnetic resonance imaging disclosed a 10-cm-diameter, lobulated, heterogeneous, locally invasive mass in the anterior skull base and cranial fossa. Initial laboratory testing showed a prolactin level of 164.5 ng/mL (normal range, 1.6 to 18.8). The pathology specimen from his surgical debulking procedure was consistent with prolactinoma. Retesting of the original serum prolactin sample with serial dilutions revealed a prolactin level of 26,000 ng/mL. A postoperative diluted prolactin level was 22,000 ng/mL. Both prolactin samples demonstrated the hook effect. dopamine agonist therapy was initiated, and the prolactin level and size of the tumor decreased substantially. The hook effect most commonly occurs when excess antigen (for example, prolactin) is present during testing. Dilution testing can counteract this assay phenomenon. CONCLUSION: Clinicians should be aware of this laboratory phenomenon when evaluating large pituitary or parasellar masses. When the hook effect is suspected, dilution testing of prolactin samples may prevent incorrect diagnosis and unnecessary surgical intervention in patients with prolactinomas.- - - - - - - - - - ranking = 1keywords = giant (Clic here for more details about this article) |
2/6. The hook effect in prolactin immunoassays.We describe a young female patient with giant invasive sellar and suprasellar tumor and modest elevation of prolactin to 165 ng/ml (normal range 3-29). A diagnosis was made of non functional pituitary adenoma with stalk effect, causing moderate prolactin elevation. A surgery for the removal of the tumor was advised but the patient declined. Treatment with a dopamine agonist was not offered. The patient presented 2 years later with deterioration of her vision and serum prolactin of >16000 ng/ml. Debulking transsphenoidal surgery was performed. The staining of tissue confirmed prolactinoma. Medical treatment with bromocriptine was initiated. We believe that the discrepancy between the 2 values of serum prolactin, is most probably caused by a hook effect in the initial prolactin assay. The mechanism of the hook effect and its occurrence with prolactin immunoassays and methods to eliminate this effect is discussed. Hook effect needs to be suspected in every patient with a giant pituitary or parasellar mass and serum prolactin <200 ng/ml. Assaying a diluted serum will usually unmask this phenomenon and allow accurate diagnosis and management.- - - - - - - - - - ranking = 1keywords = giant (Clic here for more details about this article) |
3/6. Giant invasive pituitary prolactinoma with falsely low serum prolactin: the significance of 'hook effect'.The authors report a case of a patient with giant, invasive skull base tumor extending to the parasellar area discovered incidentally during the work-up for decreased memory. The patient's neurological exam was otherwise unremarkable. Endocrine evaluation performed at a local hospital showed a moderate hyperprolactinemia 103 ng/ml (normal up to 20 ng/ml). Given the large size of the tumor, the elevated prolactin (PRL) was interpreted to be secondary to stalk effect and patient underwent debulking surgery through a transcranial approach. Immunostaining of the excised tumor tissue was strongly positive for prolactin. His prolactin was found to be 13,144 ng/ml in our lab after surgery confirming the diagnosis of invasive giant prolactinoma. The patient developed a complete right third, fourth and sixth nerve palsy postoperatively. He was started on Cabergoline with normalization of his prolactin level and more than 50% decrease in residual tumor size over 9 months periods. There has been no clinically significant improvement in his right eye ophthalmoplegia since surgery. This case highlights the importance of 'Hook Effect' resulting in falsely low prolactin level, which may have significant therapeutic implication.- - - - - - - - - - ranking = 1keywords = giant (Clic here for more details about this article) |
4/6. Giant cell tumour of the sphenoid bone with coincidental galactorrhoea--a case report.A case of the rare giant cell tumour involving the sphenoid bone is reported. The usual presentation of these tumours is headache and cranial nerve deficits. This 25-year-old lady presented with oligomenorrhoea and galactorrhoea. Investigations demonstrated an asymptomatic erosive mass lesion in the sphenoid with suprasellar extension and extension into the nasopharynx. The tumour was partially resected via the transphenoidal route. The differential diagnosis and treatment of these lesions are discussed.- - - - - - - - - - ranking = 0.5keywords = giant (Clic here for more details about this article) |
5/6. Mammosomatotroph adenoma of the pituitary associated with gigantism and hyperprolactinemia. A morphological study including immunoelectron microscopy.A 29-year old giantess with growth hormone excess and hyperprolactinemia underwent transsphenoidal surgery to remove her pituitary tumor. Electron microscopy revealed a mammosomatotroph adenoma composed of one cell type. Immunoelectron microscopy, using the immunogold technique, demonstrated predominantly growth hormone or prolactin or a varying mixture of both growth hormone and prolactin in the adenoma cells. The presence of growth hormone and prolactin was found not only in the cytoplasm of the same adenoma cells but also in the same secretory granules. In the nontumorous adenohypophysis, somatotrophs and lactotrophs showed ultrastructural signs of hyperactivity. This finding is in contrast with the presence of suppressed somatotrophs and lactotrophs seen in nontumorous portions of adult pituitaries harboring growth hormone or prolactin-secreting adenomas. Our morphological study reinforces the view that growth hormone-producing pituitary tumors, originating in childhood, are different from those of the adult gland.- - - - - - - - - - ranking = 0.5keywords = giant (Clic here for more details about this article) |
6/6. magnetic resonance imaging in the diagnosis of idiopathic giant-cell granulomatous hypophysitis: a rare cause of hyperprolactinaemia.Idiopathic giant cell granulomatous hypophysitis is a rare disorder of pituitary gland characterised by a chronic inflammatory process. It can also be an extremely rare cause of hyperprolactinaemia. In this paper, we present our experience with two cases of idiopathic giant cell granulomatous hypophysitis manifested by hyperprolactinaemia, and their neuroradiological evaluation including preoperative MRI studies in one of them, and discuss our findings in the light of the literature.- - - - - - - - - - ranking = 3keywords = giant (Clic here for more details about this article) |