In short the answer is: if you are older it quite probably does shrinks the frontal lobes.
About those frontal lobes from Wikipedia:
The executive functions of the frontal lobes involve the ability to recognize future consequences resulting from current actions, to choose between good and bad actions (or better and best), override and suppress unacceptable social responses, and determine similarities and differences between things or events.
The frontal lobes also play an important part in retaining longer term memories which are not task-based. These are often memories associated with emotions derived from input from the brain’s limbic system. The frontal lobe modifies those emotions to generally fit socially acceptable norms.
And from the study:
The National Institutes of Health study looked at women from the Women’s Health Initiative Memory Study, which is a subset of the largest study of hormone replacement therapy. The study found that, overall, women taking the hormones had smaller frontal brain lobes than women who did not follow the treatment.
“Older women who took these [hormones] … they had greater brain atrophy in these brain regions that are critical for the maintenance of memories,” said Susan Resnick, a senior investigator at the National Institute on Aging, Laboratory of Personality and Cognition, and the study’s primary author.
It may be that HRT accelerates what brain decline had already started and clearly more research is needed – BUT – this study, added to other not-so-good-stuff about the effects of HRT would make me think hard and long about HRT as an option.
I like using all of my frontal lobes and want them to stay as they are – [or even grow if that’s possible]