SUN-093 - Prolactinomas with Sdhx Mutations

Succinate dehydrogenase (SDH) gene mutations are associated with a predisposition for the development of hereditary pheochromocytomas and paragangliomas (PPGLs). The association between SDHB/SDHC mutations and prolactinoma (PRLoma) is not well established, and optimal management remains unclear.
A 55-year-old female presented for assessment of a parasellar lesion and hyperprolactinemia in the context of a known SDHB mutation (c.72+1G>T). Blood pressure had been well controlled with telmisartan 20 mg once daily. Repeated testing of urine and plasma metanephrines showed mildly elevated urine normetanephrines to a maximum of 5.7 mol/d ( < 4.3 mol/d). A Ga-68-DOTATATE PET/CT and FDG PET/CT showed an intensely FDG avid lesion centered along the left cavernous sinus with low DOTATATE uptake (Krenning’s score 1-2). An MRI sella showed a left parasellar mass (3.1x2.4x2.2 cm) with left cavernous invasion and no optic chiasm compression. Her pituitary panel revealed an elevated prolactin of 486 g/L with suppressed LH and FSH. An MIBG scan showed no uptake at the site of the mass. Given high suspicion for a PRLoma, bromocriptine 1.25 mg once daily was started. Her prolactin decreased by 60% within 7 weeks. After a switch to cabergoline 0.25 mg twice weekly due to side effects, her prolactin normalized.
A 46-year-old male presented for paraganglioma screening in the context of a positive family history of paraganglioma with an SDHC mutation (c.403+1G>T). He had no personal history of hypertension or symptoms of catecholamine excess. His plasma metanephrines and normetanephrines were normal. Genetic testing identified the same SDHC mutation. A screening MRI sella revealed a 3x5x6 mm lesion in the inferior right pituitary gland with mild rightward deviation of the infundibulum. His pituitary panel revealed a mildly elevated prolactin of 38.6 g/L ( < 21.0 g/L), testosterone 8.8 nmol/L (8-35 nmol/L), LH 2.9 IU/L ( < 12 IU/L) and FSH 6.4 IU/L ( < 7 IU/L). The pituitary lesion did not demonstrate uptake on F-DOPA PET/CT. Given the suspicion for a microPRLoma, he was treated with cabergoline 0.25 mg once weekly and prolactin decreased by 24% within 4 months. Cabergoline was increased to 0.5 mg twice weekly and prolactin normalized.
These cases highlight rare SDHB- and SHDC- related PRLomas and their responsiveness to dopamine agonist therapy. Genetic testing should be considered in patients with isolated pituitary tumours and a family history of PPGLs.

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