Apparent hypopituitarism secondary to Cushings syndrome due to adrenal carcinoma
Sarah Revesz, Andrew Knox & Bijay Vaidya
A 75-year-old lady presented with hypertension, weight gain, ankle oedema and proximal myopathy. She had clinical features of Cushings syndrome. Blood pressure was 180/99 mmHg. Her visual fields were normal. Investigations confirmed Cushings syndrome with high 24-hour free urinary cortisol levels (2264 nmol/l and 3295 nmol/l; normal range 40305) and a high serum cortisol level following overnight dexamethasone suppression test (serum cortisol 1,550 nmol/l). Further investigations showed fasting blood glucose 8 mmols/l, FSH 0.4 iu/l, LH 0.1 iu/l, oestradiol 207 pmol/l, growth hormone 0.2 iu/l, IGF1 5.6 nmol/l (636), prolactin 621 mu/l (0630), TSH 2.23 mu/l (0.354.5), FT4 7.5 pmol/l (1126), basal ACTH <5 ng/l (040), 17-OH progesterone 7.8 nmol/l, androstendione 13.1 nmol/l (312), DHEAS 4.2 μmol/l (05), testosterone 4.2 nmol/l (0.22.9), and normal 24 hour urinary 5H1AA and catecholamines. Serum cortisol did not suppress following a high dose dexamethasone suppression test (serum cortisol 1401 nmol/l). Chest x-ray was normal. In view of the biochemical hypopituitarism in addition to low ACTH, she underwent pituitary MRI as well as CT of the adrenal glands. MRI pituitary showed no abnormalities, but CT showed a 9.6×7.3 cm left adrenal mass. She underwent a left adrenalectomy; histology confirmed adrenocortical carcinoma. Following the surgery, her urinary cortisol levels normalised, and clinical symptoms of Cushings syndrome improved. Two months post-surgery, investigations showed resolution of her hypopituitarism with TSH 6.27 mu/l, FT4 12.6 pmol/l, IGF1 22.4 nmol/l, growth hormone 9.3 miu/l, FSH 64.2 iu/l, LH 38 iu/l and prolactin 709 mu/l. Short synacthen test 4 months after the surgery showed a normal response (basal serum cortisol 446 nmol/l, 30 minutes 800 nmol/). This case illustrates that apparent hypopituitarism can occur in the presence of severe hypercortisolaemia, and we hypothesize that this is due to the effect of cortisol on hypothalmo-pituitary axes.