help button home button Endocrine Society JCEM JCEM Call for Nominations for EIC
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Submit a related Letter to the Editor
Right arrow Purchase Article
Right arrow View Shopping Cart
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Copyright Permission
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Raivio, T.
Right arrow Articles by Jänne, O. A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Raivio, T.
Right arrow Articles by Jänne, O. A.
The Journal of Clinical Endocrinology & Metabolism Vol. 89, No. 3 1188-1192
Copyright © 2004 by The Endocrine Society

Serum Androgen Bioactivity in Adolescence: A Longitudinal Study of Boys with Constitutional Delay of Puberty

Taneli Raivio, Leo Dunkel, Sanna Wickman and Olli A. Jänne

Biomedicum Helsinki, Institute of Biomedicine/Physiology (T.R., O.A.J.), and Department of Clinical Chemistry (O.A.J.), University of Helsinki, FIN-00014 Helsinki, Finland; and Hospital for Children and Adolescents (T.R., L.D., S.W.), University of Helsinki and Helsinki University Central Hospital, FIN-00029 Helsinki, Finland

Address all correspondence and requests for reprints to: Taneli Raivio, M.D., Ph.D., Biomedicum Helsinki, Institute of Biomedicine (Physiology), University of Helsinki, P.O. Box 63 (Haartmaninkatu 8), FIN-00014 Helsinki, Finland. E-mail: taneli.raivio{at}helsinki.fi.


   Abstract
Top
 Abstract
Introduction
 Patients and Methods
 Results
 Discussion
 References
 
We have examined the relationship between serum androgen bioactivity, as measured with a recombinant cell bioassay, and progression of puberty in 14 boys with constitutional delay of puberty. Six boys were followed up without treatment (control group), and eight boys received low-dose (1 mg/kg) testosterone enanthate im for 0–6 months together with an aromatase inhibitor, letrozole, 2.5 mg orally once a day for 0–12 months (treatment group). In the control group, serum androgen bioactivity increased during the course of puberty (P < 0.001). During 0–12 months of the study, the boys in the treatment group had higher androgen bioactivity levels (P < 0.05) and faster rate of pubic hair growth than the control boys (P < 0.05). Overall, the average serum androgen bioactivity during 12 months of follow-up correlated strongly with the concomitant changes in Tanner genital (rS = 0.89; n = 13; P < 0.005) and pubic hair stages (rS = 0.79; n = 13; P < 0.01). In conclusion, our results suggest that circulating androgen bioactivity mediates the tempo of pubertal maturation and that the combination of testosterone and letrozole given to boys with constitutional delay of puberty accelerates puberty.


   Introduction
Top
 Abstract
 Introduction
Patients and Methods
 Results
 Discussion
 References
 
WE HAVE RECENTLY developed a recombinant cell bioassay that is based on androgen-dependent interaction between the ligand-binding domain (LBD) and the amino-terminal region of the androgen receptor (AR) and that is capable of measuring androgen bioactivity directly from human serum (1). A clear benefit of the assay is its potential capability of measuring the total androgen bioactivity brought about by different steroids present in a serum sample. By the use of this bioassay, we have demonstrated suppressed circulating androgen bioactivity in infant boys with cryptorchidism (2) and in adult men with prostatic cancer (3) and supraphysiological androgen bioactivity in men on 5{alpha}-dihydrotestosterone (DHT) treatment for symptoms of partial androgen deficiency of the aging male (4). The only postnatal period in life that is characterized by unequivocal genital development induced by androgens is puberty, but the relationship between circulating androgen milieu and virilization during that time is not known. In the current work, we have investigated this relationship in adolescent boys with constitutional delay of puberty. The boys were either followed up without treatment or received a low dose of testosterone enanthate in combination with an aromatase inhibitor, letrozole. This treatment regimen induces high serum testosterone as a result of attenuated estrogen-mediated inhibition of gonadotropin secretion, and thus, it offers a model to investigate the effect of prolonged hyperandrogenism on physical changes of puberty (5).


   Patients and Methods
Top
 Abstract
 Introduction
 Patients and Methods
Results
 Discussion
 References
 
Patients and study design

The diagnostic criteria, study protocol together with clinical data and parts of hormonal data have been described previously (1, 5, 6, 7, 8). In the current work, we initially measured androgen bioactivity levels longitudinally in seven boys who had decided to wait for spontaneous progression of puberty (control group) and in eight subjects who received low-dose testosterone enanthate in combination with the aromatase inhibitor letrozole (treatment group). The boys were clinically examined, and a venous blood sample was obtained at the beginning of the study (0 months) and 2, 5, 12, and 18 months thereafter. Puberty was assessed according to Tanner (9). One of the control boys differed completely from the other six by displaying a decrease in serum androgen bioactivity and testosterone during the follow-up (data not shown), and he was therefore excluded from the study. In the remaining control boys, five serum samples were available in five boys and four samples in one boy. Boys in the treatment group received a low dose of testosterone enanthate (Testoviron-Depot-250, Schering, Berlin, Germany) (1 mg/kg im every 4 wk) treatment for 6 months in combination with the specific and potent, fourth-generation aromatase inhibitor letrozole (Femar, Novartis AG, Stein, Switzerland; commercially purchased from hospital pharmacy), 2.5 mg orally once a day for 12 months (5). These boys were followed up with the same intervals as the control boys. The blood sample at 2 months was obtained approximately 7 d after the third testosterone injection, and the blood sample at 5 months approximately 7 d after the sixth testosterone injection. Informed written consent was obtained from the patients and from their guardians. The protocol was approved by the Ethical Committee of the Hospital for Children and Adolescents and the National Agency for Medicines.

Biochemical measurements

All the venous blood samples were drawn between 0730 and 1015 h. Blood was allowed to clot and serum was separated by centrifugation and stored at -20 C and -70 C. Serum testosterone, DHT, dehydroepiandrosterone, and androstenedione concentrations were measured by RIA after separation of steroid fractions on a Lipidex-5000 microcolumn (Packard-Becker, B.V. Chemical Operations, Groningen, The Netherlands) (5, 10). SHBG concentrations were measured by using a time-resolved fluoroimmunoassay (Perkin-Elmer Life Sciences, Turku, Finland) with inter- and intraassay coefficients of variation both less than 5% according to the manufacturer. Serum free androgen index was calculated as serum testosterone/SHBG x 100. Serum LH concentrations were measured by using ultrasensitive immunofluorometric assay (5). The recombinant cell androgen bioassay was carried out as previously described (1). In short, COS-1 cells were transiently transfected with plasmids encoding the LBD and the amino-terminal region of the AR. The presence of androgen results in the interaction of the two receptor-derived polypeptides, and the interaction is amplified by a steroid receptor coactivator, AR-interacting protein 3, also ectopically expressed in COS-1 cells. Human serum (10 µl) in duplicate was added directly to the culture medium, and the relative reporter gene (luciferase) activity measured from cell lysates reflects androgen bioactivity in human serum. Sensitivity of the assay was 0.8 nM testosterone equivalents. Bioactivities less than 0.8 nM testosterone equivalents were set equal to this limit.

Statistical analyses

Because the same subjects were investigated repeatedly, we employed the method of summary measures (11). Arithmetic means of androgen bioactivity, steroid levels, or SHBG measured at 0, 2, 5, and 12 months of the study were calculated for each individual. These average values were then used as raw data in statistical tests (one boy with missing values was excluded from these analyses) (11). ANOVA for repeated measures was used when appropriate. Mann-Whitney U test was employed to compare the changes in Tanner stages between the control group and the treatment group. Unpaired and paired t tests were used to assess differences between means when appropriate; serum LH levels (5) were log transformed into normality before testing. Relationships between two related variables were investigated with Pearson’s correlation coefficients or Spearman rank correlation when appropriate. Statistical significance was accepted for P < 0.05.


   Results
Top
 Abstract
 Introduction
 Patients and Methods
 Results
Discussion
 References
 
Individual serum androgen bioactivity values together with clinical stages of puberty in the control and treatment groups are shown in Fig. 1Go. In the control boys (subjects 1–6), serum androgen bioactivity and Tanner genital (G) stages proceeded in a parallel fashion. This was particularly obvious in subjects 1–5 (Fig. 1AGo). Subject 6 had low androgen bioactivity up to 12 months, and he displayed only some growth of pubic hair during the whole follow-up (Fig. 1AGo). Overall, the increase in serum androgen bioactivity in the five control boys with complete data series during the 18 months of follow-up from (mean ± SD) 1.1 ± 0.4 to 3.4 ± 1.5 nM testosterone equivalents was significant (ANOVA, P < 0.001). Boys in the treatment group (subjects 7–14) received low-dose testosterone enanthate together with peroral letrozole for the first 6 months of the study and thereafter only peroral letrozole up to 12 months of the study. Collectively, these subjects displayed variable patterns of androgen bioactivity during the treatment (Fig. 1BGo). Subjects 7–10 exhibited a relatively long time period from the onset of the treatment with testosterone and letrozole to the peak of androgen bioactivity, whereas subjects 11–14 displayed a substantial increase in androgen bioactivity already at 2 months of the study (Fig. 1BGo). At the start of the study, serum LH levels (mean ± SD) did not differ between subjects 7–10 and 11–14 [2.4 ± 1.3 IU/liter vs. 2.6 ± 1.4 IU/liter; P = not significant (NS)]. At 2 months, however, subjects 7–10 had lower LH levels than subjects 11–14 (2.9 ± 1.5 IU/liter vs. 13.5 ± 9.7 IU/liter; P < 0.05). All boys in the treatment group displayed supranormal serum androgen bioactivity at 12 months of the treatment (Fig. 1BGo). Letrozole administration was ceased after 12 months of the study; at 18 months of the follow-up, androgen bioactivity had declined to 3.7 ± 0.9 nM testosterone equivalents.



View larger version (25K):
[in this window]
[in a new window]
  		FIG. 1. A, Serum androgen bioactivity and G and P stages in six boys (subjects 1–6) with constitutional delay of puberty during 18 months of follow-up; B, serum androgen bioactivity and G and P stages in eight boys (subjects 7–14) with constitutional delay of puberty treated with im low-dose testosterone enanthate (0–6 months) and peroral aromatase inhibitor letrozole (0–12 months) as described in Patients and Methods (5 ). In all boys, blood samples were taken at 0, 2, 5, 12, and 18 months; in the treatment group, the samples were taken approximately 7 d after the third and the last testosterone injections, respectively (1 5 6 7 8 ). Dotted vertical lines in B indicate changes in medication. Testo, Testosterone; letro, letrozole.

 
The distribution of boys at different G stages (number of subjects) at 0 months was G2 (13) and G3 (1) and at 12 months of the study was G2 (1), G3 (6), G4 (4), and G5 (3). The corresponding distributions for pubic hair (P) stages were P1 (9) and P2 (5) at 0 months of the study and P2 (5), P3 (8), and P4 (1) at 12 months. The change in P stage between 0 and 12 months of the follow-up was higher in the treatment group (n = 8) than in the control group (n = 6) (P < 0.05) whereas the change in G stage did not differ between the groups.

The relationships between the progression of puberty and circulating androgen bioactivity or androgen levels measured with RIAs during the first 12 months of the study were investigated by correlating the changes in G or P stages that occurred during that time with the corresponding average serum hormone values. These results are shown in Table 1Go. Boys in the treatment group (n = 8) had higher average androgen bioactivity levels during the first 12 months of follow-up than those in the control group (n = 5) (6.9 ± 3.4 vs. 2.0 ± 1.1 nM testosterone equivalents, respectively; P < 0.05); the average DHT levels did not differ between the control group and the treatment group (1.7 ± 0.9 vs. 1.7 ± 0.8, respectively, P = NS). Testosterone and free androgen index were both accurate predictors of androgen bioactivity; average serum androgen bioactivity (0–12 mo) correlated strongly with average levels of serum testosterone (r = 0.92; n = 13; P < 0.0001), SHBG (r = -0.56; n = 13; P < 0.05), and free androgen index (r = 0.93; n = 13; P < 0.0001) but not with average levels of DHT (r = 0.39; n = 13; P = NS). Overall, androgen bioactivity measured at 0, 2, 5, 12, and 18 months of the study in these 13 boys correlated with testosterone (r = 0.90; n = 69; P < 0.0001), SHBG (rS = -66; n = 69; P < 0.0001), and free androgen index (r = 0.88; n = 69; P < 0.0001). Serum steroid, SHBG, and free androgen index levels during the follow-up in the control group and treatment group are summarized in Table 2Go.


View this table:
[in this window]
[in a new window]
  		TABLE 1. Spearman rank correlation coefficients between the change in G and P stages and corresponding average values for serum androgen bioactivity, serum androgen levels, and free androgen index during 12 months of follow-up in 13 boys with constitutional delay of puberty

 

View this table:
[in this window]
[in a new window]
  		TABLE 2. Serum androgen (nM), SHBG (nM), and free androgen index levels (mean ± SD) in 14 boys with constitutional delay of puberty during 18 months of follow-up (1 5 6 7 8 )

 

   Discussion
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Discussion
References
 
During the recent years, novel recombinant cell bioassays that are capable of quantifying steroid hormone bioactivity from human serum have been introduced (1, 12, 13, 14, 15). With regard to evaluating target tissue exposure to hormonal compounds, cell bioassays provide several potential benefits in comparison to methods that employ antibodies or mass spectrometry. For example, the latter two methods are unable to differentiate between steroid hormone receptor agonists and antagonists, and they cannot account for different biological activities of steroid hormones. A clinically useful recombinant cell bioassay is expected to mimic steroid hormone actions in target tissues. To the best of our knowledge, current results show for the first time that androgen-dependent changes during puberty are tightly connected with the circulating androgen bioactivity measured with the bioassay that is based on the interaction between the amino-terminal region and the LBD of AR (1). We hypothesize that, with the aid of this bioassay, it will be possible to monitor functional consequences of androgen exposure in subjects receiving naturally occurring or synthetic androgens for hypogonadism (16), improvement of working memory (17), or male contraception (18, 19).

We investigated the relationship between androgen bioactivity and the growth of pubic hair or genital development. Boys receiving the aromatase inhibitor letrozole displayed functional hyperandrogenism and faster growth of pubic hair than the control boys, and in all boys, average serum androgen bioactivity correlated with the rate of genital and pubic hair growth. The development of male external genitalia during puberty is mainly dependent on the action of androgens and the GH-IGF axis (20). In a previous study, however, we showed that serum IGF-1 and IGF-binding protein 3 levels did not increase in the control group or in the treatment group during the first 12 months of the study (5), suggesting that the genital and pubic hair development observed in the current work were mainly mediated via AR. In pubic skin, the effect of bioavailable testosterone is probably augmented, because this area predominantly harbors 5{alpha}-reductase type I enzyme (21), the expression of which is thought to be induced by androgens (reviewed in Ref. 21). The type II enzyme is essential for the development of male external genitalia in utero by converting testosterone to DHT, although a direct effect of bioavailable testosterone on genital virilization has also been suggested (22). During puberty, 46,XY patients with a mutated 5{alpha}-reductase type II enzyme gene display virilization, an effect attributed to circulating DHT (23, 24). However, our results suggest that serum DHT plays a minor role in genital growth during adolescence. By contrast, progression of puberty was tightly coupled to circulating androgen bioactivity, and average serum androgen bioactivity and testosterone correlated strongly. These findings suggest that bioavailable testosterone mainly determines the genital and pubic hair growth in puberty.

We have previously shown that letrozole treatment increases final height of boys with constitutional delay of puberty (5, 25). These boys often experience severe psychosocial stress related to their delayed puberty, and therefore, the puberty-promoting effect achieved by testosterone and letrozole was important. The relative roles of exogenous testosterone administration and endogenous testosterone synthesis stimulated by letrozole via diminished inhibition of gonadotropin secretion in the genital and pubic hair development remain unknown. Exogenous testosterone was used in this study, because the boys requested medical intervention for their delayed puberty and, at the time of the study design, it was not clear how much aromatase inhibition would augment endogenous gonadotropin and testosterone secretion. All boys in the treatment group had supranormal androgen bioactivity at 12 months, at the time when only letrozole was given, suggesting that even letrozole monotherapy may induce hyperandrogenism and virilization in pubertal boys.

When the boys received both letrozole and testosterone, their serum androgen bioactivity levels varied substantially. The reason for this remains unclear. In prepuberty, GnRH-secreting neurons are suppressed via neuronal mechanisms, and subsequently, GnRH secretion is low (26). On the other hand, androgen-mediated regulation of gonadotropin secretion in boys is operative already in early puberty (27, 28). Therefore, the low LH and androgen bioactivity levels in subjects 7–10 during the first few months of the study may reflect persisting prepubertal inhibition of GnRH secretion, suppression of GnRH secretion in response to an increase in circulating androgen bioactivity, or both.

Serum testosterone exhibits marked diurnal variation, but in the current work, single serum samples were used to estimate each individual’s prevailing hormone and androgen bioactivity levels during the first 12 months of the work. It may be questioned whether this method accurately reflects 24-hr profiles of the measured parameters in boys. However, we have previously shown that nocturnal variation in serum LH levels persists even during letrozole treatment (6), and the samples in the current work were taken in the morning within a relatively short time window, which should render the results comparable within and between the subjects. The finding that serum SHBG in the treatment group did not display any decline between 5 and 12 months of the study suggests that SHBG is not an optimal marker of prolonged androgen action during aromatase inhibition with letrozole. We have previously shown that serum insulin levels decreased in the treatment group during letrozole, whereas there was no change or an increase in the controls (7). Because insulin is at least as important as androgens and estrogens in the regulation of circulating SHBG concentration, the changes in insulin may have masked the effects of changes in serum sex steroids on SHBG.

In conclusion, circulating androgen bioactivity measured with the recently developed recombinant cell bioassay is closely correlated to androgen-dependent changes in phenotype during puberty. The combination of testosterone and letrozole induces functional hyperandrogenism that accelerates puberty, which is a common desire by the patients warranting medical intervention for their delayed onset and/or progression of puberty.


   Footnotes
 
This work was supported by grants from the Medical Research Council (Academy of Finland), National Technology Agency (TEKES), Helsinki University Central Hospital, and Foundation for Pediatric Research, Helsinki, Finland.

Abbreviations: AR, Androgen receptor; DHT, 5{alpha}-dihydrotestosterone; G, Tanner genital; LBD, ligand-binding domain; P, Tanner pubic hair.

Received October 8, 2003.

Accepted December 1, 2003.


   References
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Discussion
 References
 

  1. Raivio T, Palvimo JJ, Dunkel L, Wickman S, Jänne OA 2001 Novel assay for determination of androgen bioactivity in human serum. J Clin Endocrinol Metab 86:1539–1544[Abstract/Free Full Text]
  2. Raivio T, Toppari J, Kaleva M, Virtanen H, Haavisto AM, Dunkel L, Jänne OA 2003 Serum androgen bioactivity in cryptorchid and noncryptorchid boys during the postnatal reproductive hormone surge. J Clin Endocrinol Metab 88:2597–2599[Abstract/Free Full Text]
  3. Raivio T, Santti H, Schatzl G, Gsur A, Haidinger G, Palvimo JJ, Jänne OA, Madersbacher S 2003 Reduced circulating androgen bioactivity in patients with prostate cancer. Prostate 55:194–198[CrossRef][Medline]
  4. Raivio T, Tapanainen J, Kunelius P, Jänne OA 2002 Serum androgen bioactivity during 5{alpha}-dihydrotestosterone treatment in elderly men. J Androl 23:919–921[Abstract/Free Full Text]
  5. Wickman S, Sipilä I, Ankarberg-Lindgren C, Norjavaara E, Dunkel L 2001 A specific aromatase inhibitor and potential increase in adult height in boys with delayed puberty: a randomized controlled trial. Lancet 357:1743–1748[CrossRef][Medline]
  6. Wickman S, Dunkel L 2001 Inhibition of P450 aromatase enhances gonadotropin secretion in early and midpubertal boys: evidence for a pituitary site of action of endogenous E. J Clin Endocrinol Metab 86:4887–4894[Abstract/Free Full Text]
  7. Wickman S, Saukkonen T, Dunkel L 2002 The role of sex steroids in the regulation of insulin sensitivity and serum lipid concentrations during male puberty: a prospective study with a P450-aromatase inhibitor. Eur J Endocrinol 146:339–346[Abstract]
  8. Wickman S, Kajantie E, Dunkel L 2003 Effects of suppression of estrogen action by the P450 aromatase inhibitor letrozole on bone mineral density and bone turnover in pubertal boys. J Clin Endocrinol Metab 88:3785–3793[Abstract/Free Full Text]
  9. Tanner JM 1962 Growth at adolescence, 2nd ed. Oxford, UK: Blackwell Scientific Publications
  10. Apter D, Jänne O, Karvonen P, Vihko R 1976 Simultaneous determination of five sex hormones in human serum by radioimmunoassay after chromatography on Lipidex-5000. Clin Chem 22:32–38[Abstract]
  11. Matthews JN, Altman DG, Campbell MJ, Royston P 1990 Analysis of serial measurements in medical research. BMJ 300:230–235[Medline]
  12. Klein KO, Baron J, Colli MJ, McDonnell DP, Cutler GB 1994 Estrogen levels in childhood determined by an ultrasensitive recombinant cell bioassay. J Clin Invest 94:2475–2480[Medline]
  13. Raivio T, Palvimo JJ, Kannisto S, Voutilainen R, Jänne OA 2002 Transactivation assay for determination of glucocorticoid bioactivity in human serum. J Clin Endocrinol Metab 87:3740–3744[Abstract/Free Full Text]
  14. Paris F, Servant N, Terouanne B, Sultan C 2002 Evaluation of androgenic bioactivity in human serum by recombinant cell line: preliminary results. Mol Cell Endocrinol 198:123–129[CrossRef][Medline]
  15. Paris F, Servant N, Terouanne B, Balaguer P, Nicolas JC, Sultan C 2002 A new recombinant cell bioassay for ultrasensitive determination of serum estrogenic bioactivity in children. J Clin Endocrinol Metab 87:791–797[Abstract/Free Full Text]
  16. Anderson RA, Martin CW, Kung WC, Everington D, Pun TC, Tan KCB, Bancroft J, Sundaram K, Moo-Young AJ, Baird DT 1999 7{alpha}-Methyl-19-nortestosterone maintains sexual behavior and mood in hypogonadal men. J Clin Endocrinol Metab 84:3556–3562[Abstract/Free Full Text]
  17. Ross JL, Roeltgen D, Stefanos GA, Feuillan P, Kushner H, Bondy C, Cutler Jr GB 2003 Androgen-responsive aspects of cognition in girls with Turner syndrome. J Clin Endocrinol Metab 88:292–296[Abstract/Free Full Text]
  18. Gu Y-Q, Wang X-H, Xu D, Peng L, Cheng L-F, Huang M-K, Huang Z-J, Zhang G-Y 2003 A multicenter contraceptive efficacy study of injectable testosterone undecanoate in healthy Chinese men. J Clin Endocrinol Metab 88:562–568[Abstract/Free Full Text]
  19. Handelsman DJ 2003 Editorial: hormonal male contraception–lessons from the east when the eastern market fails. J Clin Endocrinol Metab 88:559–561[Free Full Text]
  20. Yoshizawa A, Clemmons DR 2000 Testosterone and insulin-like growth factor (IGF) I interact in controlling IGF-binding protein production in androgen-responsive foreskin fibroblasts. J Clin Endocrinol Metab 85:1627–1633[Abstract/Free Full Text]
  21. Mestayer CH, Berthaut I, Portois M-C, Wright F, Kuttenn F, Mowszowicz I, Mauvais-Jarvis P 1996 Predominant expression of 5{alpha}-reductase type 1 in pubic skin from normal subjects and hirsute patients. J Clin Endocrinol Metab 81:1989–1993[Abstract]
  22. Hiort O, Schütt SM, Bals-Pratsch M, Holterhus P-M, Marschke C, Struve D 2002 A novel disruptive mutation in the SRD5A2-gene in a partially virilized patient with 5{alpha}-reductase deficiency. Int J Androl 25:55–58[CrossRef][Medline]
  23. Peterson RE, Imperato-McGinley J, Gautier T, Sturla E 1977 Male pseudohermaphroditism due to steroid 5{alpha}-reductase deficiency. Am J Med 62:170–191[CrossRef][Medline]
  24. Thigpen AE, Silver RI, Guileyardo JM, Casey ML, McDonnell JD, Russell DW 1993 Tissue distribution and ontogeny of steroid 5{alpha}-reductase isozyme expression. J Clin Invest 92:903–910[Medline]
  25. Dunkel L, Hero M, Wickman S 2003 Inhibition of P450 aromatase in adolescent boys increases final adult height. Hormone Res 60(Suppl 2):34 (Abstract)
  26. Delemarre-van De Waal HA 2002 Regulation of puberty. Best Pract Res Clin Endocrinol Metab 16:1–12[CrossRef][Medline]
  27. Keenan BS, Richards GE, Ponder SW, Dallas JS, Nagamani M, Smith ER 1993 Androgen-stimulated pubertal growth: the effects of testosterone and dihydrotestosterone on growth hormone and insulin-like growth factor-I in the treatment of short stature and delayed puberty. J Clin Endocrinol Metab 76:996–1001[Abstract]
  28. Santen RJ, Kulin HE, Loriaux DL, Friend J 1976 Spironolactone stimulation of gonadotropin secretion in boys with delayed adolescence. J Clin Endocrinol Metab 43:1386–1390[Abstract]



This article has been cited by other articles:


Home page
 Hum Reprod UpdateHome page
P. Roy, M. Alevizaki, and I. Huhtaniemi
In vitro bioassays for androgens and their diagnostic applications
Hum. Reprod. Update, January 1, 2008; 14(1): 73 - 82.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Submit a related Letter to the Editor
Right arrow Purchase Article
Right arrow View Shopping Cart
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Copyright Permission
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Raivio, T.
Right arrow Articles by Jänne, O. A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Raivio, T.
Right arrow Articles by Jänne, O. A.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Endocrinology Endocrine Reviews J. Clin. End. & Metab.
Molecular Endocrinology Recent Prog. Horm. Res. All Endocrine Journals