What is Hypothalamic Amenorrhea (HA) - The Science Behind
In this post I go through the science behind Hypothalamic Amenorrhea. In the sister post What is Hypothalamic Amenorrhea (HA)? I explain what it is, what the symptoms are and how you can recover from it.
So what is Hypothalamic Amenorrhea? Hypothalamic Amenorrhea, or HA, is when a you lose your period due to interferences with your so called Hypothalamic-Pituitary-Ovarian (HPO) axis function. But before we dive in to the HPO-axis, lets introduce the main actors involved in the process:
Cortisol: A hormone that your adrenal glands (endocrine glands on top of your kidneys) produce and release. It affects several aspects of your body and mainly helps regulate your body's response to stress.
Estrogens: A group of hormones that play an important role in reproduction. It is produced by the ovaries. Among others it helps the ovum to mature during the first half of your cycle. It both inhibits and stimulates the production of GnRH, LH and FSH, depending on concentration.
Follicle Stimulating Hormone (FSH): Reproductive hormone made by the pituitary gland responsible for the maturation of the egg follicles in the ovary.
Hypothalamus: Small part of our brain that regulates our sleep, hunger, body temperature and our cycle. It can be thought about as our control center, responsible for homeostasis in the body.
Gonadotropin-Releasing Hormone (GnRH): Reproductive hormone made by the hypothalamus responsible for releasing LH and FSH.
Luteinizing hormone (LH): Reproductive hormone made by the pituitary gland responsible for stimulating ovulation.
Pituitary gland, a.k.a. Hypophysis: A small, pea-sized gland located below the hypothalamus. It is referred to as the body's 'master gland' because it controls the activity of most other hormone-secreting glands. It releases LH and FSH into the bloodstream.
Progesterone: A hormone released by the corpus luteum in the ovary during the second half of the cycle. It plays an important role in the cycle and in maintaining the early stages of pregnancy.
The Hypothalamic-Pituitary-Adrenal (HPA) axis
The Hypothalamic-Pituitary-Adrenal (HPA) axis (left in the picture) refers to the communication between each of these areas of the body. The HPA axis is responsible for regulating your stress levels, mood, emotions, digestion, immune system, metabolism, energy levels, and more. Things like low calorie intake, under-nutrition (also called low energy availability or energy deficiency), stress, and excessive exercise can cause significant stress on your body which leads to production of cortisol.
The Hypothalamic-Pituitary-Ovarian (HPO) axis
The Hypothalamic-Pituitary-Ovarian (HPO) axis (right in the picture) refers to the communication between each of these areas of the body. Thes HPO axis is responsible for regulating reproductive activity and ovarian hormones so if this communication is disrupted, it can cause you to lose your period.
Let's look a bit closer on this pathway. The hypothalamus releases the gonadotropin-releasing hormone (GnRH), sometimes it is released at shorter, sometimes at longer intervals. The hypothalamus thus acts like a pulse generator, releasing GnRH. GnRH in turn activates the production of LH and FSH in the pituitary gland. Both of these hormones are crucial for ovulation.
The HPO axis functions in a tandem with the HPA axis. By that I mean that they influence each other. The purpose of this is for the body to ensure both reproductive viability (HPO axis) and survival (HPA axis), to maintain homeostasis in the body. In the case of Hypothalamic Amenorrhea, the hypothalamus slows or stops releasing GnRH as a response of stress in form of high levels of cortisol (produced by the HPA axis). And less GnRH means less LH, FSH and estrogen, which means no ovulation.
I hope this post could answer the question what is Hypothalamic Amenorrhea for you. Eating too few carbs or calories and experiencing chronic stress leads to stress on your body. Your body responses to this stress by producing cortisol. The cortisol (from the PHA axis) can significantly disrupt your HPO axis and lead to you losing your period. This because the hormones involved in the onset of ovulation GnRH, LH, FSH, estrogen (HPO axis) are all inhibited by cortisol (HPA axis). For this reason, lower levels of FSH and LH are often measured in the blood for someone with Hypothalamic Amenorrhea. Estrogen can also be too low in Hypothalamic Amenorrhea.
Picture credits: the picture in this post is a modification of a picture found here: How Stress Can Contribute to Reproductive Hormone Imbalances (wildcraftmedicine.com)