Pergamon
Therapy of Cushing’s Syndrome with Steroid Biosynthesis Inhibitors
D. Engelhardt* and M. M. Weber Medical Department II, Klinikum Großhadern, University of Munich, 81377 München, Germany
Several substances with different inhibitory effects on adrenal steroid biosynthesis were investigated in patients with Cushing’s syndrome. It has been shown that trilostane, a 38-hydroxysteroid- dehydrogenase inhibitor, is not potent enough to block cortisol biosynthesis in patients with hypercortisolism. Aminoglutethimide inhibits side chain cleavage of cortisol synthesis, but it has been demonstrated that the blocking effect on cortisol secretion is not strong enough to normalize urinary cortisol excretion in patients with Cushing’s disease. For metyrapone, an inhibitor of adrenal 118-hydroxylase, promising results were reported for the treatment of Cushing’s syndrome. However, the drug has several side effects and depending on the definition of the desired reduction of cortisol secretion a true remission was only found in a minority of patients. The antifungal drug ketoconazole in vitro predominantly blocks 17,20-desmolase (IC50 1 uM) and to a lesser extent 17a-hydroxylase (IC50 10 uM) and 11-hydroxylase (IC50 15-40 uM). Therefore, ketoconazole in vivo most potently suppresses androgen secretion and only to a lesser extent cortisol biosynthesis. Several therapeutic trials with ketoconazole treatment in patients with pituitary Cushing’s disease showed various remission rates between 30 and 90%. In contrast, in almost all patients with benign, primary adrenal Cushing’s syndrome cortisol levels were normalized. In patients with ectopic ACTH syndrome ketoconazole was effective in about 50% of all reported cases, while cortisol hypersecretion due to adrenocortical carcinoma was only rarely inhibited by ketoconazole. The main side effect of ketoconazole treatment was liver toxicity which occurred in 12% of all treated patients. In contrast to ketoconazole, the narcotic drug etomidate shows a strong inhibitory effect on 118-hydroxylase (IC50 0.03-0.15 µM) but only a weak inhibition of 17,20 desmolase (IC50 380 uM). This correlates with in vivo studies where even low, non-hypnotic doses of etomidate induced a pronounced fall in serum cortisol levels in normals and in patients with Cushing’s syndrome. However, its clinical use is limited by its mandatory intravenous application and its sedative effects. In conclusion, ketoconazole remains the only available steroid-inhibitory drug for a therapeutic trial in patients with Cushing’s syndrome who cannot be treated definitively by surgery.
J. Steroid Biochem. Molec. Biol., Vol. 49, No. 4-6, pp. 261-267, 1994
INTRODUCTION
Definitive surgical treatment is the therapy of choice in all forms of Cushing’s syndrome; however, the out- come of surgical treatment largley depends on the etiology of the cortisol excess. A pituitary hypersecre- tion of ACTH (Cushing’s disease) is found in 80% of all Cushing’s syndromes and can be cured by transphe- noidal pituitary microsurgery in about 80% of all
patients. A primary adrenal cause of the hypercorti- solism (unilateral adenoma, primary bilateral hyper- plasia, carcinoma) contributes to 10% of all Cushing’s syndromes. Except for rare cases with adrenocortical carcinoma most of these patients can be cured by a uni- or bilateral adrenalectomy. In about 10% of all patients, an ectopic, non-pituitary secretion of ACTH by a benign or malign tumor can be found but often the tumor is inoperable or cannot be located. Radiation therapy of the pituitary shows an effect only after several months or years and is effective only in a group of patients with persistent Cushing’s disease. There- fore, about one-third of all patients with Cushing’s syndrome require temporary or permanent medical
*Correspondence to D. Engelhardt.
Abbreviations: ACTH, adrenocorticotropic hormone; IC50, drug concentration producing 50% inhibition in vitro.
treatment [1]. Out of the different available classes of potential therapeutic agents (steroidogenic blocking drugs, adrenolytic drugs, neuromodulatory drugs and steroid receptor antagonists) steroid biosynthesis in- hibitors have the greatest importance. This paper will give an overview about the role of steroidogenic block- ing agents in the treatment of Cushing’s syndrome, based on published data in the literature as well as on our own in vitro and in vivo studies.
TRILOSTANE
Trilostane, an androstane-carbonitrile derivative, selectively blocks in vitro the 3ß-hydroxysteroid-45,4- isomerase system, which converts pregnenolone to pro- gesterone [2]. Unfortunately, the clinical results in patients with Cushing’s syndrome are disappointing. Only 3 of 13 treated patients showed a biochemical response, so this drug cannot be recommended [3, 4].
AMINOGLUTETHIMIDE
Aminoglutethimide, an anticonvulsant drug, inhibits in vitro the side chain cleavage of cholesterol to preg- nenolone [5]. However, treatment of 39 patients with Cushing’s disease only in 18 patients resulted in a complete remission [6]. Similarly, when combined with metyrapone treatment a normalization of urinary corti- sol excretion was only found in 3 out of 6 patients with different forms of Cushing’s syndrome [7].
METYRAPONE
The pyridine derivative metyrapone at low concen- trations inhibits the transformation of 11-deoxycorti- costerone to corticosterone (11ß-hydroxylase) and at higher concentrations the side chain cleavage of choles- terol [8, 9]. In a recent study 91 patients with different forms of Cushing’s syndrome were treated with metyrapone [10]. The authors reported a very good response to metyrapone treatment with remissions in 40/53 patients with Cushing’s disease, 12/15 patients with adrenocortical tumors and in 17/17 patients with ectopic ACTH syndrome. However, they defined the therapeutic target range of mean serum cortisol levels/24 h to be <400 nmol/l (14.3 µg/dl). This is in contrast to the criteria of Orth and Liddle [11, 12] who define curative treatment from Cushing’s syndrome with mean cortisol levels of <280 nmol/l (10 µg/dl). When this therapeutic target range is applied to the data of Verhelst et al. [10] metyrapone treatment is effective only in 10/53 patients with Cushing’s disease, 7/15 patients with adrenocortical tumors and 4/17 patients with ectopic ACTH syndrome. Several side effects were observed during metyrapone treatment, especially hirsutism (16/43), dizziness (12/91) as well as edema, hypokalemia, nausea and rash [10]. Clinical data from other groups about the efficacy of
metyrapone in patients with Cushing’s syndrome are difficult to interpret because of concomitant treatment with aminoglutethimide or valproate [7,13].
KETOCONAZOLE
In 1983 we reported [14] that ketoconazole treatment (600 mg/day) in a patient with a cortisol producing adrenocortical adenoma induced a sharp fall in serum cortisol levels below 2.5 µg/dl. Incubation studies with tissue slices from this tumor and rising concentrations of ketoconazole resulted in a dose-dependent decrease of cortisol production in vitro. Further extensive incu- bation studies with human adrenocortical tissue slices and labeled precursors showed an inhibitory effect of the antimycotic imidazole derivative ketoconazole on the following adrenal enzymes: most potently keto- conazole blocked the C17,20-desmolase (conversion of 17a,20x-dihydroxyprogesterone to androstenedione) with an IC50 of 1 uM and to a lesser extent 17x - hydroxylase (conversion of progesterone to 17x - hydroxyprogesterone) with an IC50 of 10 AM and the 11ß-hydroxylase (conversion of 11-deoxycortisol to cortisol; IC50 was 15-40 AM), 16x- and 18-hydroxyl- ase. No inhibition was found for the 21-hydroxylase and 3B-hydroxysteroid-45,4-isomerase activity [15, 16]. In analogy to these in vitro data the adminis- tration of ketoconazole (600 mg/day) in patients with normal adrenocortical function induced a pronounced rise of serum levels of 17x-hydroxyprogesterone, 11- deoxycortisol, 11-deoxycorticosterone and cortico- sterone, but only a slight fall of serum cortisol (Fig. 1) [17]. In 15 patients with hyperandrogenism treatment with ketoconazole induced a fall in serum levels of dehydroepiandrosterone-sulfate (DHEA-S), dehy- droepiandrosterone (DHEA), androstenedione and tes- tosterone by 30-50% while cortisol levels were reduced by only 19% (Fig. 2) [18]. Thus in vitro and in vivo the blocking effect of ketoconazole on androgen
ng/ml
ng/ml
10
before after
8
6
4
400
2
200
17-OH-P
S
DOC
B
F
DHEAS
DHEA
Androstenedione
150
150
150
serum level %
100
100
100
50
50
50
0
0
0
0
week
1
0
week
1
0
week
1
Testosterone
Cortisol
Progesterone
150
150
1000
800
serum level %
100
100
600
400
50
50
200
0
0
0
0
week
1
0
week
1
0
week
1
biosynthesis is much more pronounced than the inhi- bition of cortisol biosynthesis.
For the treatment of Cushing’s syndrome several therapeutic trials with ketoconazole have been pub- lished [19-30]. Table 1 summarizes the results of ketoconazole treatment in 82 patients with Cushing’s
disease. The rate of remissions due to the treatment, based on normalization of free cortisol in the 24-h urine, varied between 25 and 93%. The average remis- sion rate was 70% and the response to ketoconazole did not seem to be time- or dose-dependent. The main side effect was liver toxicity which occurred in about 12%
| Authors | n | Dose mg | Duration w, m, y | Normalization urine cortisol | Side effects |
|---|---|---|---|---|---|
| Loli et al., 86 | 7 | 600-800 | 3 m | 3/7 | 0/8 |
| McCance et al., 87 | 6 | 800 | -1 w | 5/6 | 3/6 Liver toxicity |
| Diop et al., 89 | 5 | 800-1200 | 8 m | 1/5 | 0/5 |
| Cerdas et al., 89 | 7. | 600 | 1 w | 7/7 | 1/7 Liver toxicity |
| 3/7 Oedema | |||||
| Tabarin et al., 91 | 4 | 400-1200 | 4 w-6 m | 1/4, 4/4 | 0/4 |
| Mortimer et al., 91 | 8 | 800 | 2 w | 8/8 | 2/8 Liver toxicity |
| Sonino et al., 91 | 28 | 400-800 | 3 w-3 y | 26/28 | 4/34 Liver toxicity |
| Engelhardt et al., 89, 93 | 17 | 600 | 1 w-1 y | 6/17 | 3/29 Liver toxicity |
| 57/82 (70%) | 16/108 (15%) |
3 — Ex
Pat.L.I. before K.
250000
THE
relative intensity
200,000
3B-E7 I.S.
C22
C24
Cortolon
THF
150,000
Andro
100,000
Androstandiol
11-Ketoetiocholanolon
11HA o, 11KH-Keto
B-Cortolon
C32
PD
PT
5000
DHEA
a-THF
0
0
200
400
600 (Time)
Pat.L.I. after K.
400000
THE
relative intensity
300000
3B-E7 I.S.
C22
3 — Ex
PD
C24
Cortolon
B-Cortolon
THF
200,000
PT
THS
C32
100,000
A
0
0
200
400
600 (Time)
of all reported cases. In our own study with 17 patients with pituitary Cushing’s disease we found a rather disappointing remission rate of only 6/17. The insufficient suppression of cortisol biosynthesis by ketoconazole in a number of patients with Cushing’s disease might be due to an increase in ACTH se- cretion which could overcome the steroidogenic block. This hypothesis is supported by the observation that mean ACTH serum levels in 6 patients with remission during ketoconazole treatment only rose by 35%, whereas in 11 patients without normalization of uri- nary cortisol a mean increase of ACTH by 80% was found during ketoconazole therapy. A sensitive indicator for normalization of cortisol excretion is the quotient of tetrahydro-11-deoxycortisol (THS) to
tetrahydrocortisol (THF) found by gas chromato- graphic analysis of a 24-h urine sample. As shown in Figs 3 and 4, this THS/THF quotient was below 0.5 in a patient without response and about 10 in a patient with remission due to ketoconazole treatment.
The results of ketoconazole treatment in other forms of Cushing’s syndrome are summarized in Table 2. All 7 patients with an adrenal adenoma [19, 24, 26] and all 5 patients with primary bilateral hyperplasia [24, 26, 28] showed a normalization of uri- nary cortisol excretion during ketoconazole treatment. Furthermore, 4 out of 9 patients with an ectopic ACTH syndrome showed a remission of the cortisol excess [24-26, 29], but only 1 out of 5 patients with adrenocortical carcinoma [24, 26, 27, 30].
ETOMIDATE
The imidazole derivative etomidate is a short-acting hypnotic substance which is only effective when given intravenously. Incubation studies with human adreno- cortical tissue showed that it predominantly blocks the conversion of 11-deoxycortisol to cortisol (IC50 0.15 µM) and of 11-deoxycorticosterone to cortico- sterone (IC50 0.03 uM) by the 118-hydroxylase (Fig. 5) [16]. Thus etomidate is 10- to 100-fold more potent in inhibiting adrenal 118-hydroxylase activity than keto- conazole and is the most potent inhibitor of the adrenal enzyme system we know. The blocking effect of etomi- date and ketoconazole on adrenal 17«-hydroxylase ac- tivity is comparable with IC50 s of approx. 10 uM [16]. However, the blocking effect on the conversion of 17x-hydroxyprogesterone to androstenedione (C17,20-
desmolase activity) is much lower for etomidate (IC50 380 µ M) than for ketoconazole (IC50 1 u M, Fig. 6) [16].
Corresponding to these in vitro data, etomidate effec- tively suppressed cortisol secretion in patients with normal adrenocortical function or with hypercorti- solism. In a prospective, comparative study the effect of intravenous thiopental or etomidate on serum corti- sol and ACTH levels was tested in 9 healthy men [31]. The mean serum cortisol levels were significantly lower in individuals receiving etomidate (5.0 µg/dl) in com- parison to thiopental (90 µg/dl). Mean serum ACTH levels remained unchanged after thiopental but rose by 100% after the injection of etomidate [31]. In 5 patients with Cushing’s syndrome the infusion of non-sedating low doses of etomidate for 3 days induced a rapid fall of mean cortisol levels (from 40 to 20 µg/dl) already after 7 h to a steady-state level of about 12 µg/dl after
600000
PD
PT
Cortolon
Pat.B.R. before K.
A
THE
relative intensity
38-Et (I.S.)
3a-Et
DHEA
400000
THF
C32
C22
C24
200000
0
0
200
400
600
(Time)
PD
THS
Pat. B.R. after K.
400000
3a-Et
PT
relative intensity
3B-Et (I.S.)
C22
C24
C32
200000
THDOC
THE
P’ D
P’ olon
Cortolon
B-Cortolon
P’T
THF
A’D
a-THF
4
0
0
200
400
600
(Time)
| n | Duration w, m | Normalization urinary cortisol | |
|---|---|---|---|
| Adrenal adenoma | |||
| Loli et al., 86 | 1 | 2 m | 1/1 |
| Sonino et al., 91 | 1 | 3w | 1/1 7/7 |
| Engelhardt et al., 89, 93 | 5 | 1-3 w | 5/5 |
| Prim. adrenal hyperplasia | |||
| Oelkers et al., 86 | 1 | 4w | 1/1 |
| Sonino et al., 91 | 2 | 4 w, 5 m | 2/2 5/5 |
| Engelhardt et al., 89, 93 | 2 | 1 w, 1 m | 2/2 |
| Adrenal carcinoma | |||
| Sonino et al., 91 | 1 | 6m | 0/1 |
| Engelhardt et al., 89, 93 | 3 | 1-6 m | 0/3 1/5 |
| Sinnaeve et al., 89 | 1 | 2w | 1/1 |
| Ectopic ACTH syndrome | |||
| Sonino et al., 91 | 2 | 2, 14 m | 1/2 |
| Tabarin et al., 91 | 4 | 1-3 m | 0/4 |
| Farwell et al., 91 | 1 | 3 m | 4/9 1/1 |
| Engelhardt et al., 89 | 2 | 3, 6m | 2/2 |
120
100
control activity (%)
A
80
60
K
1C50
40
E
20
0
0.02
0.2
2.0
20
200
drug concentration (uM)
100
B
control activity (%)
80
60
IC50
K
40
20
E
0
0.02
0.2
2.0
20
200
drug concentration (u.M)
120
100
control activity (%)
80
60
E
IC50
40
20
K
0
0.2
2.0
20
200
2000
drug concentration (p.M)
3 days [32]. These data show that in analogy to the in vitro results etomidate in comparison to ketoconazole has a stronger inhibitory potency on cortisol biosyn- thesis in patients with Cushing’s syndrome. Unfortun- ately, etomidate has to be given intravenously and can therefore not be used for continuous therapy.
CONCLUSIONS
On the basis of the published data on the therapeutic use of the available steroid biosynthesis inhibitors- metyrapone, ketoconazole and etomidate-in patients with different forms of Cushing’s syndrome, we con- clude that ketoconazole seems to be the drug of choice for medical treatment of Cushing’s disease. A thera- peutical trial with ketoconazole should be attempted in patients who have non-curable forms of Cushing’s syndrome. For remission, a normalization of urinary excretion of free cortisol is desired and liver enzymes should be controlled within short intervals during therapy.
Acknowledgement -We are indebted to Prof. Dr K. Jacob Dept. Clin. Chemistry for carrying out gas chromatographic separation of uri- nary extracts.
REFERENCES
1. Miller J. W. and Crapo L .: The medical treatment of Cushing’s syndrome. Endocrine Rev. 14 (1993) 443-458.
2. Potts G. O., Creange J. E., Harding H. R. and Schane H. P .: Trilostane, an orally active inhibitor of steroid biosynthesis. Steroids 32 (1978) 257-267.
3. Dewis P., Anderson C., Bu’lock D. E., Earnshaw R. and Kelly W. F .: Experience with trilostane in the treatment of Cushing’s syndrome. Clin. Endocr. 18 (1983) 533-540.
4. Semple C. G., Beastall G. H., Gray C. E. and Thomson J. A .: Trilostane in the management of Cushing’s syndrome. Acta Endocr. 102 (1983) 107-110.
5. Dexter R. N., Fishman L. M., Ney R. L. and Liddle G. W .: Inhibition of adrenal corticosteroid synthesis by aminog-
lutethimide. Studies of the mechanism of action. J. Clin. Endocr. Metab. 27, (1967) 473-480.
6. Misbin R. I., Canary J. and Willard D .: Aminoglutethimide in the treatment of Cushing’s syndrome. J. Clin. Pharmac. 16 (1976) 473-480.
7. Thorén M., Adamson U. and Sjöberg H. E .: Aminoglutethimide and metyrapone in the management of Cushing’s syndrome. Acta Endocr. 109 (1985) 451-457.
8. Carballeira A., Fishman L. M. and Jacobi J. D .: Dual sites of human adrenal steroidogenesis: correlation of in vivo and in vitro studies. J. Clin. Endocr. Metab. 42 (1976) 687-695.
9. Lamberts S. W. J., Bons E. G., Bruining H. A. and De Jons F. H .: Differential effects of the imidazole derivatives etomidate, keto- conazole and miconazole and of metyrapone on the secretion of cortisol and its precursors by human adrenocortical cells. J. Pharmac. Exp. Ther. 240 (1987) 259-264.
10. Verhelst J. A., Trainer P. J., Howlett T. A., Perry L., Rees L. H., Grossman A. B., Wass J. A. H. and Besser G. M .: Short- and long-term responses to metyrapone in the medical management of 91 patients with Cushing’s syndrome. Clin. Endocr. 5 (1991) 169-178.
11. Orth D. N. and Liddle M. D .: Results of treatment in 108 patients with Cushing’s syndrome. New Engl. J. Med. 285 (1971) 243-247.
12. Orth D. N .: Metyrapone is useful only as adjunctive therapy in Cushing’s disease. Ann. Int. Med. 89 (1978) 128-130.
13. Nussey S. S., Price P., Jenkins J. S., Altaher A. R. H., Gillham B. and Jones M. T .: The combined use of valproate and metyrapone in the treatment of Cushing’s syndrome. Clin. Endocr. 28 (1988) 373-380.
14. Engelhardt D., Mann K., Hörmann R., Braun S. and Karl H. J .: Ketoconazole inhibits cortisol secretion of an adrenal adenoma in vivo and in vitro. Klin. Wochenschr. 61 (1983) 373-375.
15. Engelhardt D., Weber M. M., Miksch T., Abedinpour F. and Jaspers C .: The influence of ketoconazole on human adrenal steroidogenesis: incubation studies with tissue slices. Clin. En- docr. 35 (1991) 163-168.
16. Weber M. M., Lang J., Abedinpour F., Zeilberger K., Adelmann B. and Engelhardt D .: Different inhibitory effect of etomidate and ketoconazole on the human adrenal steroid biosynthesis. Clin. Invest. 71 (1993) 933-938.
17. Engelhardt D., Dörr G., Jaspers C. and Knorr D .: Ketoconazole blocks cortisol secretion in man by inhibition of adrenal 11ß- hydroxylase. Klin. Wochenschr. 63 (1985) 607-612.
18. Weber M. M., Luppa P. and Engelhardt D .: Inhibition of human adrenal androgen secretion by ketoconazole. Klin. Wochenschr. 67 (1989) 707-712.
19. Loli P., Berselli M. E. and Tagliaferri M .: Use of ketoconazole in the treatment of Cushing’s syndrome. J. Clin. Endocr. Metab. 63 (1986) 1365-1371.
20. McCance D. R., Hadden D. R., Kennedy L., Sheridan B. and Atkinson A. B .: Clinical experience with ketoconazole therapy for patients with Cushing’s syndrome. Clin. Endocr. 27 (1987) 593-599.
21. Cerdas S., Billaud L., Guilhaume B., Laudat M. H., Bertagna X. and Luton J. P .: Effets à court terme du ketoconazole dans les syndromes de Cushing. Ann. d’Endocr. 50 (1989) 489-496.
22. Diop S. N., Warnet A., Duet M., Firmin C., Mosse A. and Lubetzki J .: Traitement prolongé de la maladie de Cushing par le kétoconazole. Presse Med. 18 (1989) 1325-1328.
23. Mortimer R. H., Cannell G. R., Thew C. M. and Galligan J. P .: Ketoconazole and plasma and urine steroid levels in Cushing’s disease. Clin. Exp. Pharmac. Physiol. 18 (1991) 536-569.
24. Sonino N., Boscaro M., Paolette A., Mantero F. and Ziliotto D .: Ketoconazole treatment in Cushing’s syndrome: experience in 34 patients. Clin. Endocr. 35 (1991) 347-352.
25. Tabarin A., Navarranne A., Guérin J., Corcuff J .- B., Parneix M. and Roger P .: Use of ketoconazole in the treatment of Cushing’s disease and ectopic ACTH syndrome. Clin. Endocr. 34 (1991) 63-69.
26. Engelhardt D., Jacobs K. and Doerr H. G .: Different therapeutic efficacy of ketoconazole in patients with Cushing’s syndrome. Klin. Wochenschr. 67 (1989) 241-247.
27. Engelhardt D .: Unpublished cases, 1993.
28. Oelkers W., Bähr V., Hensen J. and Pickartz H .: Primary adreno- cortical micronodular adenomatosis causing Cushing’s syndrome. Effects of ketoconazole on steroid production and in vitro per- formance of adrenal cells. Acta Endocr. 113 (1986) 370-377.
29. Farwell A. P., Devlin J. T. and Stewart J. A .: Total suppression of cortisol excretion by ketoconazole in the therapy of the ectopic adrenocorticotropic hormone syndrome. Am. J. Med. 84 (1988) 1063-1066.
30. Sinnaeve L. J. E. and Becks G. P .: Preoperative ketoconazole therapy for adrenocortical carcinoma. Can. Med. Assoc. }. 141 (1989) 131-133.
31. Engelhardt D., Doenicke A., Suttmann H., Küpper F. J., Braun S. and Müller O. A .: Der Einfluß von Etomidat und Thiopental auf ACTH- und Cortisolspiegel im Serum Eine prospektive kontrollierte Vergleichsuntersuchung an gesunden Probanden. Anaesthesist 33 (1984) 583-587.
32. Allolio B., Schulte H. M., Kaulen D., Reincke M., Jaursch- Hancke C. and Winkelmann W .: Nonhypnotic low-dose etomi- date for rapid correction of hypercortisolaemia in Cushing’s syndrome. Klin. Wochenschr. 66 (1988) 361-364.