Initial medical management of a giant prolactinoma in a 54-year-old man presenting with severe hypogonadism — ASN Events

Initial medical management of a giant prolactinoma in a 54-year-old man presenting with severe hypogonadism (#326)

Jason Hockings 1 , Nicholas Hockings 2 , Nadia Patel 2 , Gregory Slater 2 3 , Allan Finnimore 2 , Lee Price 2 4 , Bruce Hall 1 2 5 , Gregory Hockings 2 5
  1. Princess Alexandra Hospital, Woolloongabba, Qld , Australia
  2. Greenslopes Private Hospital, Brisbane, Qld, Australia
  3. Queensland XRay, Brisbane, Qld , Australia
  4. Sullivan Nicolaides Pathology, Brisbane, Qld , Australia
  5. School of Medicine, University of Queensland, Brisbane, Qld, Australia

A 54-year-old man was referred in August 2010 for pituitary assessment after presenting with a chronic cough and severe sleep apnoea. His symptoms included headaches, weight gain, muscle weakness, impaired libido, erectile dysfunction, mood swings, irritability and reduced exercise capacity. His medical background comprised hypertension, hyperlipidaemia and reflux.

Investigations included serum prolactin (PRL), on two separate occasions, of 503,300 and 508,500 mIU/L (RR <500); macroprolactinaemia was present.  His total testosterone (T) was 1.6 nmol/L (RR 11-40), SHBG 21 nmol/L (RR 10-70), FSH <2 U/L (RR<10), LH<1 U/L (RR<9), free T4 11.4 pmol/L (RR 9-19), free T3 3.6 pmol/L (RR 2.6-6.0), TSH 1.5 mU/L (RR 0.3-5.0), GH 0.6 mIU/L, IGF-1 22 (RR 9-38), ACTH 30 ng/L (RR 9-51), cortisol 265 nmol/L (RR 160-650), FAG subunit 0.4 IU/L (RR<0.6) and 24-hour urinary free cortisol 44 nmol/day (RR 25-180).

MRI showed a giant pituitary tumour with displacement of normal pituitary tissue, no optic nerve/chiasm compression, but very marked inferior and lateral extension into the sphenoidal sinuses and surrounding the internal carotid arteries. His optic discs, visual acuity, colour vision and computerised perimetry were normal.

A diagnosis of giant prolactinoma was made and cabergoline treatment initiated, in gradually increasing dose to 0.5 mg daily. The addition of testosterone undecanoate resulted in symptomatic improvement, but was later discontinued because of high libido. Serial MRI scanning has shown no tumour growth, but minimal reduction in size.

His most recent results include PRL 60 mIU/L, total T 10.5 nmol/L, FSH 11 U/L, LH 10 U/L. The macroprolactinaemia has resolved.  He has not required maintenance therapy with glucocorticoids or thyroxine, but receives stress corticosteroids when appropriate. His anti-hypertensive medications have been ceased.

Surgery of giant prolactinomas is rarely curative and is associated with significant morbidity and mortality1. This patient may require surgical debulking, especially if he develops intolerance to, or further adverse effects from, ongoing high-dose cabergoline. He has had a very satisfactory initial clinical and biochemical response to medical therapy. Radiological evidence of significant tumour shrinkage is awaited; a further MRI scan is pending.

1Gillam MP, Molitch ME, Lombardi G, Colao A. Endocrine Reviews 2006; 27:485-534.