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IGF-1. The silent cause of man boobs?

In the bro-world of bros, when we are talking man boobs or bitch tits, the discussion is almost exclusively Estrogen, or the entirely unproven causes of “prolactin gyno” and “prog gyno” supposedly courtesy of Deca-Durabolin or Trenbolone. In other texts, I have discussed the prolactin conundrum, but that is not the topic of today. Today, I present to you an evidence based contributing cause of gynecomastia: Insulin-like Growth Factor 1.

Ever seen a fat or sloppy kid with puffy nipples, even full on major boobage? In fact, ever seen a lean teenager with little bee sting boobs also? It can be a cruel stage of puberty for these pre-pubescents and adolescents, but thankfully for most of them this gynecomastia is temporary. For some however, the only cure is surgical removal. Much the same as AAS associated gynecomastia, if the gynecomastia persists long term, then the gynecomastia can make itself at home permanently. It is unknown exactly how long this non-surgical treatment period lasts, but it is safe to say that if you notice signs of gyno, then you should be increasing you dose of aromatise inhibitor and/or running a temporary course of SERMs that target breast tissue as E2 antagonists (like Nolva). The pathophysiology in these non-AAS associated gynecomastia cases and the AAS associated cases can be quite similar. So, what are the main causes of gynecomastia then? Summary of the evidence; here they are:

1) Elevated levels of estradiol (most active form of estrogen in males) in general

2) Low testosterone to estradiol ratios. What this means is that if estradiol is not that high, but testosterone is very low, this can cause gynecomastia. A number of medications have been reported in the medical literature to cause gynecomastia due to decreases in testosterone, increases in estradiol, or both. These include:

1) Antiandrogens. These include cyproterone, flutamide, and finasteride.used to treat prostate cancer and some other conditions.

2) HIV medications. Sustiva, Atripla, and Videx have been associated with gynecomastia.
3) Anti-anxiety medications such as diazepam (Valium).
4) Tricyclic antidepressants. These include amitriptyline.
5) Glucocorticoid steroids.
6) Antibiotics.
7) Ulcer medication such as cimetidine (Tagamet).
8) Cancer treatment (chemotherapy).
9) Heart medications such as digitalis and calcium channel blockers.
10) Anabolic steroids (surprise)
11) Substances that have been reported to cause gynecomastia include alcohol, amphetamine, marijuana and heroin. Although these substances are best said to be associated with gynecomastia at best as a causal title has not yet been justified by solid data.
12) Last, but not least, another cause of gyno is elevations in estradiol and IGF-1 concomitantly. What this means is that if an estradiol score on its own would not normally produce gynecomastia in a subject, the addition of an elevation of IGF-1 could cause gynecomastia for a synergistic mechanism of action. This also means that elevations of IGF-1 on their own without the presence of elevated estradiol would not cause gynecomastia.

If you are ever wondering why your latest cycle of XYZ anabolic steroid stack is causing gynecomastia, yet in the past the exact same cycle would not have, you may want to consider IGF-1 as the culprit that is tipping things over the edge. Are you using HGH now (causes increase in IGF-1)? Are you using any GHS peptides like MK677 or CJC 1295 w/DAC? Are you using IGF-1-LR3 or DES? This may be the silent cause you have been pulling your hair out about.

Not to fear much though, as the IGF-1 elevations alone are not likely enough to keep those boobs growing. Once again, simply reducing estradiol levels to a point within reference ranges should solve the issue. I recommend to stay on the lower-medium end of the pathology reference ranges if you are sensitive to gyno. A score of 60-100 pmol/L of estradiol, measured via the LC/MS assay (aka sensitive assay) is a good target for most. Of course, with a perceivably esoteric claim like today, I am going to have to prove to the science savvy sceptics that I bare only the truth. I have linked the references for IGF-1 associated gynecomastia below. I know some reading today would have learned something new. Let me know if you have any questions about today’s blog. I would love to hear from you.



J Clin Endocrinol Metab. 2015 Oct;100(10):3752-9. doi: 10.1210/jc.2015-2836. Epub 2015 Aug 19.
A Longitudinal Study of Growth, Sex Steroids, and IGF-1 in Boys With Physiological Gynecomastia.

2)  Biomed Res Int. 2018; 2018: 8364824.

Published online 2018 May 29. doi: 10.1155/2018/8364824
Clinical and Etiological Aspects of Gynecomastia in Adult Males: A Multicenter Study.

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