steroid 17 alpha hydroxylase


Summary: A microsomal cytochrome P450 enzyme that catalyzes the 17-alpha-hydroxylation of progesterone or pregnenolone and subsequent cleavage of the residual two carbons at C17 in the presence of molecular oxygen and NADPH-FERRIHEMOPROTEIN REDUCTASE. This enzyme, encoded by CYP17 gene, generates precursors for glucocorticoid, androgen, and estrogen synthesis. Defects in CYP17 gene cause congenital adrenal hyperplasia (ADRENAL HYPERPLASIA, CONGENITAL) and abnormal sexual differentiation.

Top Publications

  1. Sharp L, Cardy A, Cotton S, Little J. CYP17 gene polymorphisms: prevalence and associations with hormone levels and related factors. a HuGE review. Am J Epidemiol. 2004;160:729-40 pubmed
    ..Further investigation of relations between genotype and hormone levels, exogenous hormone use, and markers of hormonal status may advance understanding of hormonally mediated diseases. ..
  2. Travis R, Churchman M, Edwards S, Smith G, Verkasalo P, Wolf C, et al. No association of polymorphisms in CYP17, CYP19, and HSD17-B1 with plasma estradiol concentrations in 1,090 British women. Cancer Epidemiol Biomarkers Prev. 2004;13:2282-4 pubmed
  3. Chacko P, Rajan B, Mathew B, Joseph T, Pillai M. CYP17 and SULT1A1 gene polymorphisms in Indian breast cancer. Breast Cancer. 2004;11:380-8 pubmed
    ..Such genotype analysis resulting in a high-risk profile holds considerable promise for individualizing screening, diagnosis and therapeutic intervention in breast cancer. ..
  4. Farnworth P, Stanton P, Wang Y, Escalona R, Findlay J, Ooi G. Inhibins differentially antagonize activin and bone morphogenetic protein action in a mouse adrenocortical cell line. Endocrinology. 2006;147:3462-71 pubmed
    ..In conclusion, inhibins A and B differentially antagonize the actions of activins and BMPs to control adrenocortical C(19) steroid production. ..
  5. Hong C, Thompson H, Jiang C, Hammond G, Tritchler D, Yaffe M, et al. Association between the T27C polymorphism in the cytochrome P450 c17alpha (CYP17) gene and risk factors for breast cancer. Breast Cancer Res Treat. 2004;88:217-30 pubmed
    ..Our findings suggest that the CYP17 A2 allele is associated with hormone levels, and interacts with insulin levels and diet to affect breast density levels and potentially breast cancer risk. ..
  6. Verla Tebit E, Wang Gohrke S, Chang Claude J. CYP17 5'-UTR MspA1 polymorphism and the risk of premenopausal breast cancer in a German population-based case-control study. Breast Cancer Res. 2005;7:R455-64 pubmed
    ..The finding, however, needs to be confirmed in further studies. ..
  7. Chen Y, Gammon M, Teitelbaum S, Britton J, Terry M, Shantakumar S, et al. Estrogen-biosynthesis gene CYP17 and its interactions with reproductive, hormonal and lifestyle factors in breast cancer risk: results from the Long Island Breast Cancer Study Project. Carcinogenesis. 2008;29:766-71 pubmed publisher
    ..In conclusion, the findings suggest that the CYP17 variant C allele may increase breast cancer risk in conjunction with long-term HRT use and high BMI in postmenopausal women. ..
  8. Ahsan H, Whittemore A, Chen Y, Senie R, Hamilton S, Wang Q, et al. Variants in estrogen-biosynthesis genes CYP17 and CYP19 and breast cancer risk: a family-based genetic association study. Breast Cancer Res. 2005;7:R71-81 pubmed
  9. Liu Y, Yao Z, Papadopoulos V. Cytochrome P450 17alpha hydroxylase/17,20 lyase (CYP17) function in cholesterol biosynthesis: identification of squalene monooxygenase (epoxidase) activity associated with CYP17 in Leydig cells. Mol Endocrinol. 2005;19:1918-31 pubmed

More Information


  1. Handratta V, Vasaitis T, Njar V, Gediya L, Kataria R, Chopra P, et al. Novel C-17-heteroaryl steroidal CYP17 inhibitors/antiandrogens: synthesis, in vitro biological activity, pharmacokinetics, and antitumor activity in the LAPC4 human prostate cancer xenograft model. J Med Chem. 2005;48:2972-84 pubmed
    ..In view of these impressive anticancer properties, compound 5 is a strong candidate for development for the treatment of human prostate cancer. ..
  2. Chang J, Gertig D, Chen X, Dite G, Jenkins M, Milne R, et al. CYP17 genetic polymorphism, breast cancer, and breast cancer risk factors: Australian Breast Cancer Family Study. Breast Cancer Res. 2005;7:R513-21 pubmed
    ..This emphasizes the need for replication in multiple and large population-based studies to provide convincing evidence for gene-environment interactions. ..
  3. Auchus R. Overview of dehydroepiandrosterone biosynthesis. Semin Reprod Med. 2004;22:281-8 pubmed
    ..These characteristics are illustrated by the fetal adrenal cortex and the zona reticularis, which are dedicated to the synthesis of DHEA and DHEA-sulfate...
  4. Chakraborty A, Murthy N, Chintamani C, Bhatnagar D, Mohil R, Sharma P, et al. CYP17 gene polymorphism and its association with high-risk north Indian breast cancer patients. J Hum Genet. 2007;52:159-65 pubmed
    ..160). The present findings suggest that CYP17 A2 allele gene polymorphism might play a significant role in breast cancer development in young Indian women. ..
  5. Einarsdóttir K, Rylander Rudqvist T, Humphreys K, Ahlberg S, Jonasdottir G, Weiderpass E, et al. CYP17 gene polymorphism in relation to breast cancer risk: a case-control study. Breast Cancer Res. 2005;7:R890-6 pubmed
    ..It is unlikely that CYP17 c.1-34T>C has a role in breast cancer etiology, overall or in combination with established non-genetic breast cancer risk factors. ..
  6. Du J, Liang X, Zeng H, Shu Y, Yao S, Zhu B, et al. Effect of small interfering RNAs of cytochrome P450 17alpha-hydroxylase/17,20-lyase (CYP17) on androgen biosynthesis in theca cells. Cell Biol Int. 2008;32:469-72 pubmed publisher
    ..RNAi effectively reduced the expression of exogenous CYP17 in HeLa cells by up to 50%. The CYP17 mRNA and androstenedione production of theca cells were slightly, but not significantly, reduced when compared with non-specific siRNA...
  7. Miyoshi Y, Iwao K, Ikeda N, Egawa C, Noguchi S. Genetic polymorphism in CYP17 and breast cancer risk in Japanese women. Eur J Cancer. 2000;36:2375-9 pubmed
    ..96, 95% CI: 0.56-1.63). These results suggest that CYP17 polymorphism(1931T/C) would be useful in the selection of Japanese women at a high risk for developing breast cancer at the age of > or = 55 years. ..
  8. Dunning A, Dowsett M, Healey C, Tee L, Luben R, Folkerd E, et al. Polymorphisms associated with circulating sex hormone levels in postmenopausal women. J Natl Cancer Inst. 2004;96:936-45 pubmed
    ..Genetic variation in CYP19 and SHBG contributes to variance in circulating hormone levels between postmenopausal women, but low r2 values may explain why these genes have given inconclusive results in breast cancer case-control studies. ..
  9. Artamonov V, Liubchenko L, Shabanov M, Babenko O, Nemtsova M, Zaletaev D. [Association of polymorphism of genetic markers of CYP19 and CYP17 with sporadic breast cancer]. Mol Biol (Mosk). 2003;37:975-82 pubmed
    ..5% vs. 20.2%, P = 0.04). Risk of BC was especially high in the presence of both factors (7.3% vs. 0%, P < 0.01). Allele (TTTA)8 and genotype A2/A2 were assumed to be risk factors of BC. ..
  10. Lin C, Martens J, Miller W. NF-1C, Sp1, and Sp3 are essential for transcription of the human gene for P450c17 (steroid 17alpha-hydroxylase/17,20 lyase) in human adrenal NCI-H295A cells. Mol Endocrinol. 2001;15:1277-93 pubmed
    ..Thus, Sp1 and Sp3 binding to the -227/-184 site and NF-1C proteins binding to the -107/-85 and the -178/-152 sites are crucial for adrenal transcription of the human gene for P450c17. ..
  11. Miyoshi Y, Ando A, Ooka M, Shiba E, Taguchi T, Tamaki Y, et al. Association of CYP17 genetic polymorphism with intra-tumoral estradiol concentrations but not with CYP17 messenger RNA levels in breast cancer tissue. Cancer Lett. 2003;195:81-6 pubmed
  12. Martin R, Lin C, Costa E, de Oliveira M, Carrilho A, Villar H, et al. P450c17 deficiency in Brazilian patients: biochemical diagnosis through progesterone levels confirmed by CYP17 genotyping. J Clin Endocrinol Metab. 2003;88:5739-46 pubmed
  13. Spurdle A, Hopper J, Dite G, Chen X, Cui J, McCredie M, et al. CYP17 promoter polymorphism and breast cancer in Australian women under age forty years. J Natl Cancer Inst. 2000;92:1674-81 pubmed
    ..48 (95% CI = 1.13-10.74; P: =.04), which is equivalent to a cumulative risk of 16% to age 70 years. The CC genotype may modify the effect of other familial risk factors for early-onset breast cancer. ..
  14. Haiman C, Hankinson S, Colditz G, Hunter D, De Vivo I. A polymorphism in CYP17 and endometrial cancer risk. Cancer Res. 2001;61:3955-60 pubmed
    ..9%; P = 0.05) and estradiol (+8.5%; P = 0.17). These data suggest that the A2 allele of CYP17 decreases endometrial cancer risk, but has only weak effects on endogenous estrogen levels among postmenopausal women. ..
  15. Wu A, Seow A, Arakawa K, Van Den Berg D, Lee H, Yu M. HSD17B1 and CYP17 polymorphisms and breast cancer risk among Chinese women in Singapore. Int J Cancer. 2003;104:450-7 pubmed
    ..41, 95% CI=1.56-3.72; RR=4.39, 95% CI=1.71-11.30, respectively). The latter gene-parity effects were especially pronounced in postmenopausal women. ..
  16. McKean Cowdin R, Feigelson H, Pike M, Coetzee G, Kolonel L, Henderson B. Risk of endometrial cancer and estrogen replacement therapy history by CYP17 genotype. Cancer Res. 2001;61:848-9 pubmed
    ..31; 95% CI, 0.53-3.21). These preliminary findings suggest that CYP17 or other variants in estrogen biosynthesis or metabolism pathways may be potential markers of endometrial cancer susceptibility due to ERT. ..
  17. Hsu C, Yang Y, Lian S, Lee S, Shin S, Tsai J, et al. Significantly increased cortisol secretion in normal adrenocortical cells transfected with K-ras mutants derived from human functional adrenocortical tumors. DNA Cell Biol. 2001;20:231-8 pubmed
    ..The K-ras oncogene significantly increases cortisol secretion by normal adrenocortical cells. ..
  18. Daneshmand S, Weitsman S, Navab A, Jakimiuk A, Magoffin D. Overexpression of theca-cell messenger RNA in polycystic ovary syndrome does not correlate with polymorphisms in the cholesterol side-chain cleavage and 17alpha-hydroxylase/C(17-20) lyase promoters. Fertil Steril. 2002;77:274-80 pubmed
    ..Overexpression of CYP17 and CYP11A mRNA in theca cells from polycystic ovaries is explained by polymorphic differences in the gene promoters. ..
  19. Feigelson H, McKean Cowdin R, Henderson B. Concerning the CYP17 MspA1 polymorphism and breast cancer risk: a meta-analysis. Mutagenesis. 2002;17:445-6; author reply 447-8 pubmed
  20. Feigelson H, McKean Cowdin R, Coetzee G, Stram D, Kolonel L, Henderson B. Building a multigenic model of breast cancer susceptibility: CYP17 and HSD17B1 are two important candidates. Cancer Res. 2001;61:785-9 pubmed
    ..29-7.25). These findings suggest that breast cancer risk has a strong genetic component and supports the theory that the underlying mechanism of "complex traits" can be understood using a multigenic model of candidate genes. ..
  21. Ye Z, Parry J. The CYP17 MspA1 polymorphism and breast cancer risk: a meta-analysis. Mutagenesis. 2002;17:119-26 pubmed
    ..The OR for age at menarche (> or = 13) was 0.87 (95% CI 0.62-1.17). Our results suggest that CYP17 MspA1 polymorphism may be at best a weak modifier of breast cancer risk but is not a significant independent risk factor. ..
  22. Gudmundsdottir K, Thorlacius S, Jonasson J, Sigfusson B, Tryggvadottir L, Eyfjord J. CYP17 promoter polymorphism and breast cancer risk in males and females in relation to BRCA2 status. Br J Cancer. 2003;88:933-6 pubmed
    ..Our findings do not indicate a role for the CYP17 T-C polymorphism in female breast cancer, but a role in male carriers of a BRCA2 mutation could not be excluded because of the small sample size. ..
  23. Hefler L, Tempfer C, Grimm C, Lebrecht A, Ulbrich E, Heinze G, et al. Estrogen-metabolizing gene polymorphisms in the assessment of breast carcinoma risk and fibroadenoma risk in Caucasian women. Cancer. 2004;101:264-9 pubmed
    ..Although the authors were not able to develop interaction models involving SNPs, they did provide evidence that CYP1A1 is a low-penetrance susceptibility gene with respect to breast carcinoma in a large series of Caucasian women. ..
  24. Heikkilä M, Peltoketo H, Leppäluoto J, Ilves M, Vuolteenaho O, Vainio S. Wnt-4 deficiency alters mouse adrenal cortex function, reducing aldosterone production. Endocrinology. 2002;143:4358-65 pubmed
    ..In summary, these results point to a role for Wnt-4 in adrenal gland development and function. ..
  25. Ambrosone C, Moysich K, Furberg H, Freudenheim J, Bowman E, Ahmed S, et al. CYP17 genetic polymorphism, breast cancer, and breast cancer risk factors. Breast Cancer Res. 2003;5:R45-51 pubmed
  26. Gorai I, Tanaka K, Inada M, Morinaga H, Uchiyama Y, Kikuchi R, et al. Estrogen-metabolizing gene polymorphisms, but not estrogen receptor-alpha gene polymorphisms, are associated with the onset of menarche in healthy postmenopausal Japanese women. J Clin Endocrinol Metab. 2003;88:799-803 pubmed
    ..A1/A1H/Hwt/wt genotypes, on ages at menarche and/or natural menopause. The results suggest that the estrogen-metabolizing CYP17 genotype influences age at menarche in healthy postmenopausal Japanese women. ..
  27. McCann S, Moysich K, Freudenheim J, Ambrosone C, Shields P. The risk of breast cancer associated with dietary lignans differs by CYP17 genotype in women. J Nutr. 2002;132:3036-41 pubmed
    ..12, 95% CI 0.03-0.50). Our results suggest that CYP17 genotype may be important in modifying the effect on breast cancer risk of exogenous estrogens, particularly for premenopausal women. ..
  28. Lai J, Vesprini D, Chu W, Jernstrom H, Narod S. CYP gene polymorphisms and early menarche. Mol Genet Metab. 2001;74:449-57 pubmed
    ..The polymorphic variants of the CYP3A4, CYP17, CYP1B1, and CYP1A2 genes are unlikely to influence age of menarche. ..
  29. Tworoger S, Chubak J, Aiello E, Ulrich C, Atkinson C, Potter J, et al. Association of CYP17, CYP19, CYP1B1, and COMT polymorphisms with serum and urinary sex hormone concentrations in postmenopausal women. Cancer Epidemiol Biomarkers Prev. 2004;13:94-101 pubmed
    ..This study provides further evidence that genetic variation may appreciably alter sex hormone concentrations in postmenopausal women not taking hormone therapy. ..
  30. Mitrunen K, Jourenkova N, Kataja V, Eskelinen M, Kosma V, Benhamou S, et al. Steroid metabolism gene CYP17 polymorphism and the development of breast cancer. Cancer Epidemiol Biomarkers Prev. 2000;9:1343-8 pubmed
    ..Because these findings are based on relatively small numbers in stratified analysis, they should, however, be interpreted with caution before being confirmed in future studies. ..
  31. Derebecka Holysz N, Lehmann T, Holysz M, Trzeciak W. SMAD3 inhibits SF-1-dependent activation of the CYP17 promoter in H295R cells. Mol Cell Biochem. 2008;307:65-71 pubmed
    ..In conclusion, our results suggest that the inhibitory action of TGF-beta on CYP17 transcription involve at least two mechanisms: SMAD3 dependent inactivation of CYP17 promoter activity and repression of SF-1 expression. ..
  32. Wei J, Wei J, Li W, Bi Y, Wei F. Genotyping of five chinese patients with 17alpha-hydroxylase deficiency diagnosed through high-performance liquid chromatography serum adrenal profile: identification of two novel CYP17 mutations. J Clin Endocrinol Metab. 2006;91:3647-53 pubmed
    ..Our studies suggest that 17alpha-hydroxylase deficiency may not be rare in the Chinese population. ..
  33. Lee Robichaud P, Akhtar M, Wright J, Sheikh Q, Akhtar M. The cationic charges on Arg347, Arg358 and Arg449 of human cytochrome P450c17 (CYP17) are essential for the enzyme's cytochrome b5-dependent acyl-carbon cleavage activities. J Steroid Biochem Mol Biol. 2004;92:119-30 pubmed
  34. Ohno S, Nakajima Y, Nakajin S. Triphenyltin and Tributyltin inhibit pig testicular 17beta-hydroxysteroid dehydrogenase activity and suppress testicular testosterone biosynthesis. Steroids. 2005;70:645-51 pubmed
    ..Based on these results, it appears possible that the effects of TBT and TPT are largely due to direct inhibition of 17beta-HSD activity in vivo...
  35. Mori K, Kizawa H, Ushiyama T, Chano T, Inoue H, Tsuchiya N, et al. Association of CYP17 with HLA-B27-negative seronegative spondyloarthropathy in Japanese males. Am J Med Genet A. 2004;130A:169-71 pubmed
    ..Haplotype analysis did not demonstrate more significant association. The CYP17 SNP is associated with SNSA in HLA-B27-negative Japanese males. ..
  36. Echiburú B, Perez Bravo F, Maliqueo M, Sanchez F, Crisosto N, Sir Petermann T. Polymorphism T --> C (-34 base pairs) of gene CYP17 promoter in women with polycystic ovary syndrome is associated with increased body weight and insulin resistance: a preliminary study. Metabolism. 2008;57:1765-71 pubmed publisher
  37. Moustafa G, Ibrahim Z, Hashimoto Y, Alkelch A, Sakamoto K, Ishizuka M, et al. Testicular toxicity of profenofos in matured male rats. Arch Toxicol. 2007;81:875-81 pubmed
    ..Furthermore, we propose that the above three steroidogenic-related genes and the gene of acrosomal reaction as potential biomarkers of testicular toxicity. ..
  38. Chen Y, Pei J. Factors influencing the association between CYP17 T34C polymorphism and the risk of breast cancer: meta-regression and subgroup analysis. Breast Cancer Res Treat. 2010;122:471-81 pubmed publisher
    ..After these population stratifications, there was evidence indicating that a possible impact of menopausal status, age at menarche, and BMI on the association between CYP17 T34C polymorphism and the risk of breast cancer. ..
  39. Wong S, Shu S, Tsai C. Seventeen alpha-hydroxylase deficiency. J Formos Med Assoc. 2006;105:177-81 pubmed
    ..Prophylactic gonadectomy was scheduled. In summary, 17OHD should be suspected in patients with hypokalemic hypertension and lack of secondary sexual development so that appropriate therapy can be implemented. ..
  40. Ergun Longmire B, Auchus R, Papari Zareei M, Tansil S, Wilson R, New M. Two novel mutations found in a patient with 17alpha-hydroxylase enzyme deficiency. J Clin Endocrinol Metab. 2006;91:4179-82 pubmed
    ..Identification of novel mutations in the CYP17 gene is vital in understanding the molecular mechanisms of its deficiency and in providing additional information about the structure and enzymatic functions of P450c17. ..
  41. He L, Yang Z, Yu H, Cheng B, Tang W, Dong Y, et al. The relationship between CYP17 -34T/C polymorphism and acne in Chinese subjects revealed by sequencing. Dermatology. 2006;212:338-42 pubmed
    ..No significant difference was observed between the female patients, mild + moderate male patients and their controls, respectively. The CYP17 -34C/C homozygote Chinese men are at a significantly increased risk of developing severe acne. ..
  42. Reid A, Attard G, Barrie E, de Bono J. CYP17 inhibition as a hormonal strategy for prostate cancer. Nat Clin Pract Urol. 2008;5:610-20 pubmed publisher
    ..The rationale for and implications of CYP17 inhibition and the CYP17-targeting agents in development are discussed in this Review. ..
  43. Setiawan V, Schumacher F, Haiman C, Stram D, Albanes D, Altshuler D, et al. CYP17 genetic variation and risk of breast and prostate cancer from the National Cancer Institute Breast and Prostate Cancer Cohort Consortium (BPC3). Cancer Epidemiol Biomarkers Prev. 2007;16:2237-46 pubmed
    ..Our findings do not support the hypothesis that common germ line variation in CYP17 makes a substantial contribution to postmenopausal breast or prostate cancer susceptibility. ..
  44. MacKenzie S, Dewar D, Stewart W, Fraser R, Connell J, Davies E. The transcription of steroidogenic genes in the human cerebellum and hippocampus: a comparative survey of normal and Alzheimer's tissue. J Endocrinol. 2008;196:123-30 pubmed publisher
    ..There is no evidence of a link between AD and altered steroid biosynthesis within human hippocampus and cerebellum. ..
  45. Parker C, Staton B, Grilliot M. Ontogeny of cytochrome B5 and cytochrome P450 C17 in the human fetal adrenal gland during normal development. Endocr Res. 2004;30:541-2 pubmed
  46. Kok H, Onland Moret N, van Asselt K, van Gils C, van der Schouw Y, Grobbee D, et al. No association of estrogen receptor alpha and cytochrome P450c17alpha polymorphisms with age at menopause in a Dutch cohort. Hum Reprod. 2005;20:536-42 pubmed
    ..No evidence was found for a relationship between common variants of the ERalpha gene and the CYP17 gene with age at natural menopause. ..
  47. Akhtar M, Kelly S, Kaderbhai M. Cytochrome b(5) modulation of 17{alpha} hydroxylase and 17-20 lyase (CYP17) activities in steroidogenesis. J Endocrinol. 2005;187:267-74 pubmed
  48. Kayani A, Glister C, Knight P. Evidence for an inhibitory role of bone morphogenetic protein(s) in the follicular-luteal transition in cattle. Reproduction. 2009;137:67-78 pubmed publisher
    ..Collectively, these findings support inhibitory roles for BMP/activin signalling in luteinization and steroidogenesis in both TC and GC. ..
  49. Attard G, Reid A, A Hern R, Parker C, Oommen N, Folkerd E, et al. Selective inhibition of CYP17 with abiraterone acetate is highly active in the treatment of castration-resistant prostate cancer. J Clin Oncol. 2009;27:3742-8 pubmed publisher
    ..CYP17 blockade by abiraterone acetate results in declines in PSA and CTC counts and radiologic responses, confirming that CRPC commonly remains hormone driven. ..
  50. Yang J, Cui B, Sun S, Shi T, Zheng S, Bi Y, et al. Phenotype-genotype correlation in eight Chinese 17alpha-hydroxylase/17,20 lyase-deficiency patients with five novel mutations of CYP17A1 gene. J Clin Endocrinol Metab. 2006;91:3619-25 pubmed
    ..F453S mutation results in partially reduced enzymatic activities and a subtle phenotype. The prevalent mutation 1517_1525del in Chinese 17OHD patients might be a founder effect. ..
  51. Krysiak R, Marek B, Okopień B. [Rare congenital defects of adrenal steroidogenesis]. Endokrynol Pol. 2008;59:354-65 pubmed
    ..Therefore, this paper discusses the etiopathogenesis, clinical manifestation, biochemical abnormalities and management of other less frequent defects of adrenal steroidogenesis. ..
  52. Ondré D, Wolfling J, Toth I, Szécsi M, Julesz J, Schneider G. Steroselective synthesis of some steroidal oxazolines, as novel potential inhibitors of 17alpha-hydroxylase-C17,20-lyase. Steroids. 2009;74:1025-32 pubmed publisher
    ..The 3-chlorophenyl- (8d), and the 4-bromophenyl-17beta-(2-oxazolin-5-yl)androst-4-en-3-one derivatives (8f) were found to be modest inhibitors (IC(50)=4.8 and 5.0 microM, respectively). ..
  53. McVey M, Cooke G, Curran I, Chan H, Kubow S, Lok E, et al. Effects of dietary fats and proteins on rat testicular steroidogenic enzymes and serum testosterone levels. Food Chem Toxicol. 2008;46:259-69 pubmed