Tag Archives: Leptin

Skinny celebrity pregnancies: a glimmer of truth

My apologies for the sparse blogging these past few months. Its been on my mind all the time, but I just hadn’t the drive or time to write great posts – and if they aren’t going to be great, I don’t want to waste your time. I have been debating on writing this post for a while, because it’s a bit more personal and very sciencey. If neither of those things interest you, you can skip it and I actually have several recipe posts lined up!

I want to talk about hormones.  I have been debating about going to medical school for quite a while now, with my interest growing at my internship at the fertility center (although I am more interested in the other branch of endocrinology, which is metabolism) and my endocrinology course. I just took the final on Tuesday and realized how in love with it I am. That’s why Im bursting at the seams to talk about female reproductive hormones.

To be blunt, I want this post to convey how the menstrual cycle works, why it is so important to have a regular cycle, the damage that amennorhea can wreak on the female body, and a bit of advice for bringing the body back to a hormonally balanced state.

To understand everything, a little anatomy is needed.

The hypothalamus is a section of the brain, composed of millions of nuclei that communicate with the rest of your body. It has centers that regulate everything, from hunger, to metabolism, to reproductive hormones, to sleeping cycles. Most importantly, when given the proper stimuli, the hypothalamus sends signals to the pituitary gland.

This depicts the hypothalamus connecting to the pituitary gland which sends hormonal signals to the rest of the body. 

The pituitary gland secretes many hormones that travel to tissues in the body and activate them to perform their necessary functions. In the case of reproductive hormones, the hypothalamus sends Gonadotropin Releasing Hormone (GnRH) to the pituitary. This causes the gonadotrope cells in the pituitary gland to secrete Follicle Stimulating Hormone (FSH) and Leutinizing Hormone (LH).

This depicts the hypothalamus connecting to the pituitary gland which then sends hormonal signals to the ovaries. LHRH is referring to GnRH.

The ovaries contain a set amount of oocytes (baby eggs) from the day you are born. At puberty, the hypothalamus begins to send enough GnRH to the pituitary which will secrete more FSH and LH which will travel to the ovaries. Once stimulated by Follicle Stimulating Hormone and Leutinizing Hormone, the oocytes begin to develop and mature further. In the monthly menstrual cycle, this is the Follicular phase. The growing follicles secrete estrogen as they mature. This estrogen causes the uterus to build up a blood lining. The follicle with the most FSH receptors continues to grow, while the others die off. After about two weeks of the follicles growing and secreting estrogen, there is a surge of LH which causes ovulation. This is the egg breaking free from the follicle, which is basically a nice little shell of hormone secreting cells. The egg is now free to hitch hike down the ovaries and try to get inseminated. Meanwhile, the empty follicle shell is transformed into the corpus luteum. This is the luteal phase of the menstrual cycle. The corpus luteum is a package of cells that begins to secrete progesterone, which maintains the lining of the uterus. Over the next two weeks, the corpus luteum secretes progesterone, but if the egg isnt fertilized, the level of progesterone falls and the lining is shed. And the cycle starts over!

Main point: No GnRH = No FSH or LH = No growing follicles or corpus luteum = No estrogen or progesterone = No period, no cycle, no babies. Nada.

And why is this relevant?

There are many things that can shut down the GnRH signal from the hypothalamus and thus cause amenorrhea. A few include..

  • High energy expenditure (like endurance athletes)
  • Stress (cortisol)
  • Melatonin (the sleepy hormone – you would have to take a shit load of this though)
  • Pregnancy and breast feeding
  • Menopause and hormonal disorders like PCOS
  • Certain medications
  • Low leptin levels

What is leptin? Leptin is a hormone that is secreted after meals to tell your brain that you are satisfied and to stop eating. It is also produced as a baseline depending on body fat levels. The more body fat you have, the more leptin. Women with very low body fat do not have enough leptin to signal the brain that they are healthy and thus will not secrete enough GnRH or FSH and LH to begin a menstrual cycle. This can be due to working out too much, not eating enough, or both. Enough body fat means that the body is healthy enough and has enough energy stores to sustain a pregnancy. The body is smart. Its not going to let you grow a fetus if you can’t even afford to not eat for a couple days. Shit happens.

So if you aren’t having a period, you can’t sustain a pregnancy. But if you don’t want to become a mother right now, then it’s no big deal, right?


Having a menses is for more important than just getting preggers. It means you have adequate estrogen, and estrogen is ABSOLUTELY ESSENTIAL for bone growth.

This shows the pathway between the brain, pituitary, ovaries, and bone destruction. 

When estrogen binds to receptors in bones, it stimulates the production of a protein called OsteoProtyGerin (OPG). OPG binds to osteoclasts (cells that break bones down) and prevents them from growing and proliferating. Thus, it has a bone protective effect. Estrogen also stimulates the production of growth hormone, which stimulates the production of IGF1. Both growth hormone and IGF1 contribute to bone growth. They are responsible for bone matrix formation, CALCIUM DEPOSITION, and bone cell proliferation and maturation. Therefore, estrogen is essential to both growing bones and preventing their breakdown. Unfortunately, bone break down is constant – we are constantly remodeling our bones to maintain adequate blood calcium levels. So estrogen is needed throughout our lives – not just for a couple years to grow our bones. Furthermore, it is now suspected that bone density is greatest between the ages of 18-25, so suffering from amenorrhea during these sensitive years could lead to a lifetime of weak bones and related complications.

The moral of this novel is that if you aren’t having a menses than you are inching closer and closer to osteoporosis and you aren’t at your healthiest state. It is important to go see an endocrinologist and see what’s up! It could be many things, and low body fat is one of the more reversible issues to work with. It doesn’t mean one has to gain tons of weight, stop working out, and eat junk. In fact, weight training helps build bones, so that should always be a part of any weight plan, whether gaining or losing!

In order to prevent bone loss during the weight gain or lifestyle change process, the endocrinologist may prescribe birth control as soon as possible. This is because the synthetic estrogens are still effective at bone synthesis. When I went in to see my endocrinologist, he also said that if I didn’t want to gain weight but I wanted to have kids later on, not to worry, there are drugs for that.

That pissed me off.

But a lightbulb went off. I had always wondered how extremely thin women, like Posh Spice and Nicole Richie had managed to have children despite their skeletor-esq bodies. Turns out, fertility drugs can override the lack of leptin (and body fat) and give you large doses of FSH to stimulate follicle growth. This is just my opinion, but it seems as though that is cheating nature. Furthermore, I worry that could possibly have effects on the child later in life. Again, this is just me playing around with ideas, but there are studies out there that indicate that babies born to mothers who were pregnant during a famine or economic depression were more likely to be overweight or obese later in life. The lack of energy (or folate or something else – I’m not sure) altered the epigenetic markings on the fetus’ DNA and thus made the future men or women more prone (but not doomed) to weight gain and resistance to weight loss. Perhaps having a child via fertility drugs when your weight and energy intake isn’t adequate could have similar effects?…

If you have any questions or want any more details, information, whateva, just send me and email or leave a comment!