Pituitary failure as a presentation of previously undiagnosed metastatic lung cancer
TM Galliford & PH Winocour
The causes of panhypopituitarism are well known and pituitary metastases is a recognised but rare cause. It can often be difficult to diagnose because the non-specific features of malignancy mask those of pituitary involvement.
We present the case of a 73 year old gentleman who complained of fatigue and weight loss. He had recently been treated for a radiographically proven bronchopneumonia. Endocrine checks suggested secondary hypothyroidism however (TSH 0.37 milliunits per litre; fT4 8.0 picomoles per litre). In addition, random cortisol was low with an attenuated response to ACTH (peak 440 nanomoles per litre). Panhypopituitarism was later confirmed (LH <1 units per litre, FSH 1 units per litre; testosterone 0.6 nanomoles per litre; PRL 539 milliunits per litre).
An MRI of pituitary gland showed a metastatic deposit in the infundibulum of the pituitary gland, and at bronchoscopy an obstruction was found at the right middle lobe entrance. Histology identified undifferentiated large cell carcinoma.
Following appropriate hormonal replacement, diabetes insipidus developed. This demonstrates that an intact adrenal axis is necessary for the expression of diabetes insipidus and that glucocorticoid replacement can unmask a relative deficiency of vasopressin.
Several aspects of this case are unusual. Firstly, pituitary metastasis is much more likely to occur in patients who are already known to have diffuse malignant disease. Secondly, our patient presented with features of anterior pituitary dysfunction, however usually there is a predilection for metastatic spread to the posterior lobe.
The commonest sites of primary neoplasms in cases of metastatic spread to the pituitary gland are lung and breast. Once detected prognosis is a few months, however diagnosis is important as hormonal replacement can improve symptoms. Furthermore, if there is concern regarding optic chiasmal compression then radiotherapy and/or debulking procedures have a low associated morbidity and have been shown to improve visual field defects.