The Authors’ Reply: Oestradiol concentrations arenot elevated in obesity-associatedhypogonadotrophic hypogonadism

We would like to thank Dhindsa and colleagues for their inter-

est and comments on our recent review article published in

Clinical Endocrinology entitled ‘The Role of Obesity and Type 2

Diabetes Mellitus in the development of Male Obesity-associated

Secondary Hypogonadism’. We would also like to thank the

Editor for the opportunity to respond. We would like to con-

firm that we agree with the useful comments raised and provide

further comment below.

In our published review, we commented that the mechanisms

implicated in the pathogenesis of secondary hypogonadism in

men and its association with obesity and type 2 diabetes mellitus

are multiple, complex and incompletely understood. We also

stated that one of the pathogenic mechanisms implicated in the

development of male obesity-associated secondary hypogona-

dism is increased aromatase activity within adipocytes. This

results in increased peripheral conversion of testosterone into

oestradiol and subsequent negative feedback on secretion of

luteinizing hormone secretion from the pituitary. The suppres-

sive effect of such a mechanism on the male hypothalamo–pitui-

tary–gonadal axis results in a reduction in plasma testosterone

levels and secondary hypogonadism. Consistent with this

hypothesis, it has been reported in the literature that obese men

show increased levels of oestrogens and decreased levels of bio-

available androgens within the serum.1 It has also been noted

that use of aromatase inhibitors in men with obesity-related

hypogonadism may normalize serum testosterone, again consis-

tent with an important pathogenic role for aromatization in this

condition.2 However, we acknowledge that there is controversy

in the literature regarding the role of aromatization in the path-

ogenesis of male obesity-associated secondary hypogonadism.

There is some inconsistency in the literature regarding relation-

ships between serum levels of testosterone and oestradiol and

the severity of obesity in this condition. We acknowledge that in

some studies on obese men, serum levels of free oestradiol

directly correlate with free testosterone.3,4 One explanation for

this direct correlation is that with increasing obesity in men, as

serum levels of testosterone fall (following suppression of the

male gonadal axis), serum oestradiol levels would also be

expected to fall eventually due to lack of substrate (testosterone)

for the aromatase enzyme. This hypothesis has been supported

by the European Male Ageing Study.3,4

We feel that it is important to emphasize that there are many

potential mechanisms that underlie the complex pathogenesis of

male obesity-associated secondary hypogonadism other than

enhanced aromatase activity, as outlined in our published review

article. These include the increasingly important roles of leptin,

inflammatory mediators (TNF-a, IL-1b, CRP), the role of sleep

disruption and the serotoninergic system and endogenous kiss-

peptin. We also outline the effects of insulin resistance at vari-

ous levels including lipases, suppression of hepatic SHBG

synthesis and the suppression of the hypothalamo–pituitary unit

as potentially important pathogenic mechanisms. There may also

be other, as yet unknown mechanisms at play. Clearly, there is a

need for further focused studies in this field to develop a clear

understanding of pathogenesis and to inform future novel treat-

ment strategies.

Saboor S. A. Aftab, Sudhesh Kumar and Thomas M. Barber

Department of Metabolic and Vascular Health, Clinical Sciences

Research Laboratories, University Hospitals Coventry and

Warwickshire, The University of Warwick, Coventry, UK

E-mail: T.Barber@warwick.ac.uk

doi: 10.1111/cen.12244

References

1 Mammi, C., Calanchini, M., Antelmi, A. et al. (2012) Androgens

and adipose tissue in males: a complex and reciprocal interplay.

International Journal of Endocrinology, 2012, 789653.

2 Loves, S., Ruinemans-Koerts, J. & de Boer, H. (2008) Letrozole

once a week normalizes serum testosterone in obesity-related

male hypogonadism. European Journal of Endocrinology, 158, 741–747.

3 Dandona, P. & Dhindsa, S. (2011) Update: hypogonadotropic

hypogonadism in type 2 diabetes and obesity. The Journal of Clin-

ical Endocrinology and Metabolism, 96, 2643–2651.4 Tajar, A., Forti, G., O’Neill, T.W. et al. (2010) Characteristics of

secondary, primary, and compensated hypogonadism in aging

men: evidence from the European Male Ageing Study. The Journal

of Clinical Endocrinology and Metabolism, 95, 1810–1818.

High circulating levels of CCL2 in patients withKlinefelter’s syndrome

Dear Sir,

Klinefelter’s syndrome, 47, XXY (KS), is the most frequent sex

chromosome aberration in males and the most common cause

of primary hypogonadism.1 The main endocrine derangements

of KS include decreased secretion of androgens, increased

plasma gonadotrophins, small testes and azoospermia.1 Patients

with KS have a higher prevalence of metabolic syndrome (MetS)

and cardiovascular abnormalities, accounting for the increased

risk of dying from heart disease.1–3 MetS is closely associated

with a low-grade chronic inflammatory status characterized by

abnormal cytokine production, which activates a network of

inflammatory signalling pathways. CCL2 is a major chemokine

produced by monocytes, dendritic cells and macrophages and is

crucial for the induction of chronic low-grade inflammation by

accelerating macrophage infiltration in adipose tissue. Overpro-

duction of CCL2 is associated with insulin resistance, the patho-

physiological basis for the development of MetS. While the high

prevalence of MetS in KS is well established, no data are avail-

able on the circulating profile of CCL2 in KS. We measured the

circulating levels of CCL2, CXCL10 and adiponectin to assess

their potential role in the development of MetS in KS.

Twenty-six young men with KS with a verified 47, XXY

karyotype were studied. Previous or current cardiovascular or

© 2013 John Wiley & Sons Ltd

Clinical Endocrinology (2014), 80, 464–467

Letters to the Editor 465

respiratory and chronic renal disease constituted exclusion crite-

ria. All patients were on replacement therapy with 1000 mg

long-lasting intramuscular testosterone every three months

(Nebido, Bayer HealthCare, Milan, Italy) with normal androgen

levels on at least two separate determinations before entering the

study. Thirty healthy young males, recruited among hospital

staff, with similar age and BMI to the KS subjects served as con-

trols. Serum testosterone, FSH, LH, SHBG, IGF-1, PRL, thyroid

hormones, TSH, insulin and routine blood tests were measured

in all patients and controls at study entry. Routine blood tests

included: triglycerides total cholesterol, LDL cholesterol, HDL

cholesterol, glucose, basal insulin, CRP and albumin. HOMA

index was calculated for each subject. CXCL10, CCL2 and

adiponectin were measured using commercially available kits

(R&D Systems). The presence of MetS was ascertained in

patients and controls according to the NCEP-ATPIII criteria.

Written informed consent was obtained from all patients and

controls. The study protocol was approved by the ethics com-

mittee of the Second University of Naples. Statistical analysis

was performed using the SPSS software (SPSS, Inc., Evanston,

IL). Values are given as mean � SD unless otherwise stated.

A P value <0�05 was considered statistically significant.

We found that KS men had significantly higher serum levels

of LH and FSH, and testosterone tended to be lower but not

statistically different in KS (16�8 � 2�0 nM) as compared with

controls (19�4 � 0�5 nM). All the other hormones were similar

between the two groups, with the exception of higher mean

levels of circulating fasting insulin and HOMA-index values in

KS compared with controls. The major difference between the

two groups was a significantly (P < 0�001) higher prevalence of

MetS in KS (50%) as opposed to controls (6�7%). Figure 1a

shows significantly higher serum levels of CCL2 in KS as

opposed to controls (591�0 � 223�6 ng/l vs 351�3 � 136�6 ng/l,

respectively; P < 0�0001). On the contrary, no significant differ-

ences in serum CXCL10 (90�6 � 38�9 ng/l vs 85�4 � 31�0 ng/l;

NS) and adiponectin (7 � 1 ng/l vs 8�8 � 4 ng/l NS) were

observed between the two groups. A positive and significant

relationship (R2 = 0�235; P < 0�05) was found between serum

levels of CCL2 and testosterone in KS (Fig. 1b). In subgroup

analysis, KS subjects were stratified according to the presence of

MetS (data not shown). The only significant difference between

the two groups was the lower levels of IGF-1 found in KS and

MetS (0�02 � 0�002 nM) as opposed to the group of KS without

MetS (0�034 � 0�004 nM), (P < 0�03).The main results of our study were: (i) the finding of signifi-

cantly higher serum CCL2 levels in KS; (ii) a positive correlation

between CCL2 and testosterone; (iii) the stratification of patients

according to the presence or absence of MetS showed similar

hormone concentrations, adiponectin, CCL2 and CXCL10 levels

in patients with KS MetS+ as opposed to KS MetS-. Adiponectin,

due to its insulin sensitizing, fat-burning, cardioprotective, anti-

inflammatory and antioxidant effects, is protective against the

development of MetS, and low circulating adiponectin concen-

trations are associated with obesity and MetS. Surprisingly, we

found similar levels of adiponectin in KS independently of the

presence of MetS and controls. Our result was similar to that of

Bojsen et al.4 but, compared with the previous report, an advan-

tage of our study is that all enrolled KS were eugonadal, avoid-

ing bias due to inclusion of hypogonadal men that could have

confounded cytokine assessments, given the known direct effects

of testosterone on pro-inflammatory cytokines or any indirect

effects mediated through muscle mass. At variance with adipo-

nectin, KS men had significantly higher serum levels of CCL2 as

compared with controls. The increased circulating concentra-

tions of CCL2 are unlikely to be due to a general inflammatory

state as the levels of CXCL10 were comparable between KS and

controls. High serum levels of CCL2 have been reported to be

associated with insulin resistance and inflammation, and our

data support a pathogenetic role of CCL2 in MetS. This hypoth-

esis could well fit with our finding of higher CCL2 serum levels

(a)

(b)

Fig. 1 Panel a: Patients with KS display a significant increase

(P < 0�0001) in the serum levels of CCL2 as compared with control

subjects. These data are expressed as median and 25th and 75th

percentiles in boxes and 5th and 95th percentiles as whiskers. Panel b: A

statistically significant positive correlation (R2 = 0�235; P < 0�05) was

found between the circulating levels of CCL2 and testosterone in

patients with KS.

© 2013 John Wiley & Sons Ltd

Clinical Endocrinology (2014), 80, 464–467

466 Letters to the Editor

in a population (patients with KS) at high risk of developing

MetS. The fact that serum levels of CCL2 were similar in KS

with or without MetS, suggests that this chemokine is more clo-

sely related to KS per se rather than to the presence of MetS.

Finally, we found a direct correlation between circulating

CCL2 and testosterone levels. In vitro studies conducted in

peripheral blood mononuclear cells and prostate cells have

shown that testosterone exerts a powerful anti-inflammatory

action, as assessed by its ability to reduce the secretion of several

cytokines and chemokines including CCL2. However, acute

testosterone deprivation in healthy men leads to an increase in

serum CCL2 levels, which is not reversed by restoration of phys-

iological circulating concentrations of testosterone. Furthermore,

the differences in the response to testosterone replacement ther-

apy in KS could be dependent upon androgen receptor signal-

ling defects.5 These findings indicate that, in addition to

hormonal factors, a genetic interaction, possibly mediated

through macrophage infiltration of adipose tissue, is involved in

the development of MetS in KS.

Mario Rotondi*, Francesca Coperchini*, Andrea Renzullo†,

Giacomo Accardo†, Daniela Esposito†, Gloria Groppelli*,

Flavia Magri*, Antonio Cittadini‡, Andrea M Isidori§,Luca Chiovato* and Daniela Pasquali†

*Unit of Internal Medicine and Endocrinology, Fondazione

Salvatore Maugeri I.R.C.C.S., Laboratory for Endocrine Disruptors

and Chair of Endocrinology University of Pavia, Pavia,

†Endocrinology and Metabolic Diseases, Department of

Cardiothoracic and Respiratory Sciences, Second University of

Naples, ‡Department of Internal Medicine, Cardiovascular Sciences

and Clinical Immunology, University Federico II, Naples and

§Department of Experimental Medicine,

Sapienza University of Rome, Rome, Italy

E-mail: daniela.pasquali@unina2.it

doi: 10.1111/cen.12245

References

1 Radicioni, A.F., Ferlin, A., Balercia, G. et al. (2010) Consensus

statement on diagnosis and clinical management of Klinefelter

Syndrome. Journal of Endocrinological Investigation, 33, 839–850.2 Rotondi, M., Fallerini, C., Pirali, B. et al. (2012) A unique patient

presenting with case report concomitant Klinefelter syndrome,

Alport syndrome, and craniopharyngioma. Journal of Andrology

33, 1155–1159.3 Pasquali, D., Arcopinto, M., Renzullo, A. et al. (2012) Cardiovas-

cular abnormalities in Klinefelter Syndrome. International Journal

of Cardiology, doi: 10.1016/j.ijcard.2012.09.215. [Epub ahead of

print].

4 Bojesen, A., Juul, S., Birkebaek, N.H. et al. (2006) Morbidity in

Klinefelter syndrome; a Danish register study based on hospital

discharge diagnoses. Journal of Clinical Endocrinology and Metabo-

lism, 91, 1254–1260.5 Ferlin, A., Schipilliti, M., Vinanzi, C. et al. (2011) Bone mass in

subjects with Klinefelter syndrome: role of testosterone levels and

androgen receptor gene CAG polymorphism. Journal of Clinical

Endocrinology and Metabolism, 96, 739–745.

© 2013 John Wiley & Sons Ltd

Clinical Endocrinology (2014), 80, 464–467

Letters to the Editor 467