What are the Causes of Gynecomastia?

The three main periods in which physiologic Gynecomastia will occur are in neonates, during or before puberty, and in old age.
The causes of this ailment are really unclear and there is no clear cause.
Some of the potential culprits appear to be medications including hormones, an increase in serum estrogen, a decrease in a testosterone production, androgen receptor defects, chronic kidney disease, chronic liver disease, HIV, and several other chronic illnesses.
There have also been reported cases of Gynecomastia occurring as the result of a spinal cord injury and also after refeeding starvation victims.
However, in 25% of all cases of Gynecomastia, the cause is simply unknown.
In post-adolescent adults it is believed that 10-20% of all cases of Gynecomastia are a direct result of medications.
Some of the medications that can cause Gynecomastia are cimetidine, spironolactone, omeprazole, imatinib mesylate, finasteride, and also some antipsychotics.
By leading to increased secretion of prolactin from the pituitary gland from the blocking of the actions of dopamine on the cell groups in the anterior pituitary known as lactotrope the development of male breasts is made possible.
Other medications such as those used to treat prostate cancer like antiandrogens and GnRH analogs are also thought to cause Gynecomastia.
Another cause that is thought to bring on Gynecomastia is marijuana usage, though published data contradicts this claim.
It is also possible that increased estrogen levels can take place in some testicular tumors as well as in hyperthyroidism.
Some adrenal tumors can cause elevated levels of androstenedione, which is then converted into estrone, which is a form of estrogen, by the enzyme aromatase.
All other forms of tumors that secrete hCG can also increase estrogen as well.
In liver cirrhosis, a decrease in estrogen clearance can occur which many also lead to Gynecomastia.
The reason obesity can lead to Gynecomastia is also in the fact that it increases estrogen levels.
In a recent study it was found that repeated application of products containing tea tree oils and lavender, as well as some other unidentified ingredients may be linked to the development of Gynecomastia in prepubescent males.
The theory behind this is that the ingredients produce estrogenic and antiandrogenic activity.
With that said, there were other circumstances surrounding the study and the sample size was limited to three individuals therefore no real scientific conclusions could be drawn.