Endocrine Abstracts

The granulation pattern of somatotroph adenoma is well known to be associated with differing clinical and biochemical characteristics and it has been shown that sparsely granulated tumors respond poorly to commonly used somatostatin analogs. We report a challenging case of acromegaly with a sparsely granulated tumor, resistant to multiple modalities of treatment given over several years and ultimately achieving biochemical control with pasireotide. A 26-year-old lady presented with classical features of acromegaly. She had no family history of pituitary tumors or hypercalcaemia. An OGTT confirmed acromegaly, IGF-1 was 1710 μg/l and mean growth hormone (GH) was >600 mU/l, indicating high disease burden. In addition, there was secondary hypogonadism, marginally elevated prolactin and hypothyroidism. MRI scan showed a 4 cm pituitary macroadenoma with suprasellar extension and right side cavernous sinus invasion. She underwent trans-sphenoidal pituitary surgery. Histology displayed moderate amounts of sparsely granular eosinophilic cytoplasm, staining only for GH. Postoperative investigations showed uncontrolled disease (IGF1-1474 μg/L, mean GH-228 mU/l) and residual tumor in the cavernous sinus. She received external beam fractionated radiation. Over the years she received octreotide LAR (up to 30 mg), lanreotide (up to 120 mg) 2 weekly, cabergoline, pegvisomant and stereotactic radiosurgery to no avail. Only pegvisomant resulted in some disease control; however this had to be stopped due to abnormal liver functions. Fifteen years after the diagnosis, she was started on pasireotide 40 mg monthly. Within a month, her IGF-1 dropped and has remained within the normal range for age (103–310 μg/l). Pasireotide was well tolerated and the patient’s symptoms improved significantly. Somatostatin receptor subtyping revealed a positivity score of two for both SST5 and SST2a subtypes.

Conclusion: Tumours that poorly respond to first generation SST, especially sparsely granulated somatotroph adenomas, can respond to pasireotide and treatment should be considered early in the management of resistant tumours.