We hear a lot of talk about hormones, but what are they actually? Hormones are chemical messengers that play a crucial role in how our bodies function. They influence everything from metabolism and appetite to stress, sleep, and reproductive health. How it works is the hormones are produced by organs of the endocrine system, and then travel through our body to communicate with specific cells and organs. Our body has over 50 hormones but here are a few prominent ones divided into three main categories.
Menstrual Cycle & Reproductive Health
Estrogen: Reproductive & Bone Health
Estrogen rises significantly during the follicular phase of menstruation and peaks just before ovulation. The rise of estrogen helps to build the uterine wall which is shed on day 1 of our cycle. Estrogen also helps maintain bone density and supports collagen production which makes it important for bone health and muscular health. Estrogen contributes to feelings of increased energy and better moods.
Progesterone: The Post-Ovulation Hormone
Progesterone rises after ovulation during the luteal phase and helps prepare the uterine lining for a potential pregnancy. If pregnancy doesn’t occur, progesterone levels fall, which contributes to the start of menstruation. Progesterone is helpful for nervous system health and can be converted into a neurosteroid, allopregnanolone, which enhances GABA signaling in the brain. It may also contribute to a slightly higher resting body temperature and some women may notice increased appetite, bloating or changes in their mood.
FSH: Follicle Development
FSH is released by the pituitary gland and stimulates the growth and development of ovarian follicles, which contain developing eggs. FSH continues to rise as the ovarian follicles grow. The follicle most responsive to FSH becomes the dominant follicle that will eventually mature and release an egg during ovulation.
Luteinizing Hormone (LH): Ovulation
LH works alongside FSH to regulate reproductive function. A surge in LH triggers ovulation, releasing the mature egg from the ovary. This hormone surge is what at-home ovulation predictor kits detect and signals the beginning of your most fertile window.
Testosterone: Muscle & Bone Health
Testosterone is present in both sexes, although women naturally produce smaller amounts. In women, testosterone supports muscle development, bone density, sex drive, and reproductive function. Levels can fluctuate throughout the menstrual cycle, with a slight increase around ovulation that may contribute to changes in sexual desire.
Hunger, Fullness & Blood Sugar
Insulin: Blood Sugar & Energy
Produced by the pancreas, insulin helps glucose move from the bloodstream into cells, where it can be used for energy or stored for later use. Insulin levels rise after eating, especially carbohydrate-rich meals, to help regulate blood sugar. Insulin is also essential for providing energy to your muscles and helping replenish glycogen stores after exercise.
Ghrelin: Hunger Signals
Often called the “hunger hormone,” ghrelin is produced in the stomach and helps signal hunger to the brain. It regulates appetite by typically rising before meals and falling after eating. Ghrelin also stimulates growth hormone release and plays a role in metabolism, energy balance, and reward pathways in the brain.
Leptin: Energy & Fulness
Leptin is produced mainly by fat cells and communicates information about the body's stored energy to the brain, helping regulate appetite over time. Leptin levels tend to decrease when you're undereating or in a prolonged calorie deficit, which can signal your brain to increase hunger and conserve energy. It also plays an important role in reproductive health by helping signal that your body has enough energy to support normal hormonal function.
GLP-1: Blood Sugar & Satiety
Glucagon-like peptide-1 (GLP-1) is released by the intestine in response to food. It helps stimulate insulin release when blood sugar is elevated, slows stomach emptying, and contributes to feelings of fullness after a meal. You may notice its effects as feeling satisfied for longer after eating.GLP-1 has also inspired a class of medications used to treat type 2 diabetes and obesity.
CCK: Fullness & Digestion
Cholecystokinin (CCK) is released by the small intestine, particularly in response to fats and proteins. It supports digestion by stimulating the release of pancreatic enzymes and bile, while also signaling fullness to help regulate meal size. It helps you feel comfortably full and slows down how quickly food leaves your stomach.
Stress & Sleep
Cortisol: Stress & Morning Energy
Produced by the adrenal glands, cortisol helps the body respond to physical and emotional stress. Levels naturally peak in the early morning to help you wake up and feel alert, then gradually decrease throughout the day. Cortisol also helps regulate blood sugar, metabolism, blood pressure, and inflammation.
Melatonin: Sleep
Melatonin is produced by the pineal gland, primarily in response to darkness. It helps regulate your sleep-wake cycle and signals when it's time to prepare for sleep. Levels naturally rise in the evening and decrease in the morning with exposure to light. Exposure to bright light, especially from screens, late at night can suppress melatonin production, making it harder for your body to recognize that it's time for sleep.
The Takeaway
While each hormone has a unique role, they all work together to keep your body running smoothly. Hormones naturally fluctuate throughout the menstrual cycle, across the day, and through the lifespan. They are the driving messengers behind daily functioning and are critical for wellbeing.
Sources
Hayes, H. (2024, July 17). What is a hormone? National Institute of General Medical Sciences. https://nigms.nih.gov/biobeat/2024/07/what-is-a-hormone
Athar, F., Karmani, M., & Templeman, N. M. (2024). Metabolic hormones are integral regulators of female reproductive health and function. Bioscience reports, 44(1), BSR20231916. https://doi.org/10.1042/BSR20231916
