Fig. 8. 7 
The aetiology of spontaneous Cushing's syndrome in 225 patients seen at St Bartholomew's Hospital between 1969 and 1991. 
Eighty-three per cent of all causes are ACTH-dependent and seventeen per cent ACTH independent. Although the most common cause is pituitary-dependent disease (Cushing's disease: sixty-six per cent of all cases of Cushing's syndrome and seventy-nine per cent of ACTH-dependent cases), ectopic ACTH production is also important (twelve per cent of all cases of Cushing's syndrome and fourteen per cent of ACTH-dependent cases). 

Fig. 8.8 
The involvement of ACTH and cortisol in the hypothalamic-pituitary-adrenal axis. 
Cortisol produced in the adrenals or by an adrenal tumour has a negative feedback effect on ACTH production. Oral steroids have the same effect. Conversely, ACTH stimulates cortisol production and secretion, as do pituitary or ectopic tumours and intramuscular injections of ACTH.  

Fig. 8.9
 Macroscopic and microscopic views of a thymic tumour. 
The whole tumour (a) is from a patient with Cushing's syndrome. The conventional histology of the tumour is shown in (b). The immunofluorescent staining in section (c) is used to reveal ACTH- containing tumour cells by staining them yellow with an anti-ACTH antibody. By courtesy of Mr GM Rees and Prof I Doniach.

Fig. 8.10 
Appearance of a patient with ectopic ACTH syndrome. 
Marked wasting and skin pigmentation are present.

Fig. 23.29 
Adrenal carcinoma: CT scan. 
This I0cm left adrenal mass shows the characteristic CT appearances of an adrenal carcinoma. Adrenal carcinomas usually measure 6cm or more at the time of presentation and show inhomogeneous enhancement following the injection of intravenous contrast medium. Enlarged lymph nodes or metastatic spread elsewhere may also be shown. This patient had a pulmonary metastasis on chest X-ray.

Fig. 8.15 
CT scan of the abdomen in Cushing's syndrome.
 The irregular lobulated mass in the position of the right adrenal was confirmed at operation to be an adrenal carcinoma. By courtesy of Dr FE White. 

Fig. 8.11 
Appearance of a patient with Nelson's syndrome. 
The gross pigmentation that occurs in this syndrome is best seen on the flexural surfaces of the body.