This idea popped into my head and I just had to write this story. With how much Sheldon likes to tease the girls about their periods, at some point he had to be curious as to why didn't like discussing the topic. This is set in season 8 in The Status Quo Combustion when Sheldon is sitting with Penny having a casual conversation. Enjoy.

To Sheldon's surprise he was actually enjoying a night with Penny. The conversation had been quite intriguing to him and he had actually opened up to her about how hard of a time he had with conversations like this. He was surprised at how much Penny had grown to be a part of the group over the years. Who would have expected a girl like her to join his friend group?

Before she left for the night it struck him that there was one more thing he was curious about. This might be the only chance he ever got to ask her.

"Penny," he asked, "Why don't you like talking about your period?"

"Where did that come from?" she asked, a little caught off guard.

"When I casually observe strangers' conversations in public locations…"

"You mean eavesdrop?" Penny interrupted.

"Yes that, I've noticed that other women often complain about their menstrual cycles, talk about the cramps and inconvenience. I've noticed that you don't and when I bring up the subject, you shut me down right away and I don't understand why."

Penny suddenly realized he really meant it. He really had no clue why anyone would not want to talk about it. She knew that he had no aversion to discussing it. He certainly brought the topic up often enough. He was also right, although she knew why she never had that conversation with him, that would just be a weird conversation to have with Sheldon of all people, she had to think for a minute or so as to why she never really talked about it with anyone else, not even the girls or Leonard. Sheldon sat patiently waiting for her answer.

"I guess it's because of how I was raised," Penny said. "In a small town like where I grew up, it wasn't something that was discussed. I'm sure you know what that's like. In conservative small towns a lot of people think it's something to be embarrassed of, so it was never talked about especially around guys. I know its not true. My mom was different. When I started she told me congratulations, nothing to be embarrassed about, but not to tell anyone. She said talking about your period was giving people one more thing they could use against you. The more I thought about it the more I realized she was right. I wouldn't say I'm embarrassed but if I talked about it people like you would try to use it against me."

Sheldon just looked at her as if expecting there was more she had to say. He was, as usual, correct.

"I guess some of it is out of respect for some girls I knew from back home," she paused remembering the girls she used to bus tables with back when she was in high school. "There was one girl I was especially close to. We used to tell each other everything. I was working with her one Thursday night and she mentioned that she had been experiencing a heavy period for almost two weeks. I told her she might want to see a doctor about that and she brushed me off. The next night was crazy, we were so busy, I was doing dishes and she was clearing and setting tables for hours without a break. After things had been wrapped up for the night and I was headed out, I saw her sitting on the floor with her head between her legs trying not to pass out. Her iron levels must have been so low that a night of work that would usually barely cause her to break a sweat had her barely awake. When I asked her if she needed a ride home, she said she was fine and for me not to worry. She probably should have gone to a doctor, I don't know if she was embarrassed or afraid they wouldn't take her seriously. Seeing something like that can change the way you think. I guess my period was always unpleasant, mildly painful, but in general completely tolerable. It's out of respect for girls like her with real health issues that I don't really talk about it. When they do go to the doctor for help, their pain and problems need to be taken seriously and that will never happen if the rest of us go around whining all the time."

Sheldon took a second to process her answer, "I guess that makes sense." He'd never thought about it like that before. "Does that mean I'm…part of the problem" he asked concerned.

Penny just laughed, "Don't worry Sheldon. I don't think anyone takes anything that comes out of your mouth to seriously.

Sheldon was about to respond but decided against it. It had been a relatively pleasant evening and he was content to leave it at that.

I've got a factory job right now and I spend all day planning my stories in my head looking forward to when I can get home and type them up. This one I was especially looking forward to. Hope you enjoyed it. If you like stories on this topic, I've got a few others mainly from Percy Jackson and Harry Potter. Thanks for reading :)