New Study: Letrozole once a week normalizes serum testosterone in obesity-related mal

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DOI: 10.1530/EJE-07-0663
European Journal of Endocrinology, Vol 158, Issue 5, 741-747
Copyright © 2008 by Society of the European Journal of Endocrinology

CLINICAL STUDIES
Letrozole once a week normalizes serum testosterone in obesity-related male hypogonadism
Sandra Loves1, Janneke Ruinemans-Koerts2 and Hans de Boer1

Departments of1 , Internal Medicine2 Clinical Chemistry, Ziekenhuis Rijnstate, Wagnerlaan 55, 6800 TA Arnhem, The Netherlands

(Correspondence should be addressed to H de Boer; Email: [email protected])

Objective: Isolated hypogonadotropic hypogonadism (IHH) is frequently observed in severely obese men, probably as a result of increased estradiol (E2) production and E2-mediated negative feedback on pituitary LH secretion. Aromatase inhibitors can reverse this process. This study evaluates whether letrozole once a week can normalize serum testosterone in severely obese men and maintain its long term effect.

Design: Open, uncontrolled 6-month pilot study in 12 severely obese men (body mass index>35.0 kg/m2) with obesity-related IHH and free testosterone levels <225 pmol/l, treated with 2.5 mg letrozole once a week for 6 months.

Results: Six weeks of treatment reduced total E2 from 123±11 to 58±7 pmol/l (P<0.001, mean±S.E.M.), and increased serum LH from 4.4±0.6 to 11.1±1.5 U/l (P<0.001). Total testosterone rose from 5.9±0.5 to 19.6±1.4 nmol/l (P<0.001), and free testosterone from 163±13 to 604±50 pmol/l (P<0.001). Total testosterone rose to within the normal range in all subjects, whereas free testosterone rose to supraphysiological levels in 7 out of 12 men. The testosterone and E2 levels were stable throughout the week and during the 6-month treatment period.

Conclusion: Letrozole 2.5 mg once a week produced a sustained normalization of serum total testosterone in obese men with IHH. However, free testosterone frequently rose to supraphysiological levels. Therefore, a starting dose <2.5 mg once a week is recommended.
 
Has anybody found a good comparison chart or writeup on the different AI's that are on the market with respect to how they compare with each other? I am just wondering if these results are specific to letro, or if you can get the same affect with 6oxo, formestane, aromasin, etc.
 
well, I know the write up for dex says it can be used for HRT and letro takes along time to kick in, but there was some other reason why I never tried it --gonna go check out the write up
 
skull said:
It puts your cholesterol levels in the craper like no other
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I wonder if this is still accurate when we are talking about a single does of 2.5 per week? rather then multiple times per week dosing like many do with AI's especially while on.

Mr.50
 
Mr.50 said:
I wonder if this is still accurate when we are talking about a single does of 2.5 per week? rather then multiple times per week dosing like many do with AI's especially while on.

Mr.50
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If you end up testing that theory I would be very intrested to see bloodwork results-I guess you would take 2.5 every day for 60 day [for it to kick in] then once a week after that--I would try myself but Im in the middle of somthing else at the moment
 
skull said:
If you end up testing that theory I would be very intrested to see bloodwork results-I guess you would take 2.5 every day for 60 day [for it to kick in] then once a week after that--I would try myself but Im in the middle of somthing else at the moment
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Hey Skull I might give it a shot but I was wondering what is the mechanism that delays Letroz effects so that you would have to take it for 60 days first? I have never heard of that?

Mr.50
 
I suspect it's a see/feel thing that has nothing to do with whether or not anything's happening, derived from the mistaken notion that hormones don't actually affect your body until the quantity /frequency / duration reaches the mythical "kick-in" point.
 
How good is this compared with Aromasin and Arimidex, it´s too other main rivals? Well, In non-cellular systems, Letrozole (Femara) is 2-5 times more potent than anastrozole and exemestane in its inhibition of the aromatase enzyme and activity, and in cellular systems it is 10-20x more potent! It also lasts quite a long time in your body,but takes awhile to get going& Letrozole (Femara) has a whopping 2-4 day (!) ½ life, and you need to take Letrozole (Femara) for 60 days to get a steady blood plasma level (8).

part of the write up-- FROM STERIODS.COM
 
skull said:
How good is this compared with Aromasin and Arimidex, it´s too other main rivals? Well, In non-cellular systems, Letrozole (Femara) is 2-5 times more potent than anastrozole and exemestane in its inhibition of the aromatase enzyme and activity, and in cellular systems it is 10-20x more potent! It also lasts quite a long time in your body,but takes awhile to get going& Letrozole (Femara) has a whopping 2-4 day (!) ½ life, and you need to take Letrozole (Femara) for 60 days to get a steady blood plasma level (8).

part of the write up-- FROM STERIODS.COM
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Wow that seems really weird that for something with such a long half life you would need to take it for so long to build up a steady blood level unless the absorbtion is so poor......
 
Doesn't matter as it is quite powerful. Evidently powerful enough to hammer down the E2 levels in the severely obese and jack their test levels. So basically, 2-4 hours is enough to bind to a significant amount of aromatase.
 
bioman said:
Doesn't matter as it is quite powerful. Evidently powerful enough to hammer down the E2 levels in the severely obese and jack their test levels. So basically, 2-4 hours is enough to bind to a significant amount of aromatase.
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Where did you get the 2-4 hr info?
 
skull said:
well, I know the write up for dex says it can be used for HRT and letro takes along time to kick in, but there was some other reason why I never tried it --gonna go check out the write up
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Most say that Letro will destroy sex drive. Arimidex seems more user friendly.
 
Mr.50 said:
I wonder if this is still accurate when we are talking about a single does of 2.5 per week? rather then multiple times per week dosing like many do with AI's especially while on.

Mr.50
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Yep -- enough to screw your lipid profile. There are several articles on the net comparing the AIs. I dont have them saved. But a search can locate them in 15 minutes. I know Good Guys has one.
 
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