Hormone Series Part 5: Oestrogen and Progesterone.

In part 4 we discussed the male steroid hormone testosterone and how this is important for both health and muscle growth. In women, the two main steroid hormones associated with health are in two main groups; the oestrogens and progestin’s, and like testosterones, these are synthesised from cholesterol in the body. Like all steroid hormones, these can pass easily through cell membranes and binds to and activates oestrogen receptors in the cell’s nucleus, which regulates many genes and the creation of proteins and enzymes. Oestrogen is released primarily from the ovaries in women, and in men small amounts are produced in various tissues in the body and can also be converted from testosterone under the action of aromatase enzymes. Like women and testosterone, a certain amount of oestrogen is required in males, and this interacts with testosterone to regulate testosterone’s effects. So a complete reduction in oestrogen in males is not likely to be a good thing for health and normal function.


Although these hormones are mainly considered in regard to their roles in the female reproductive cycle and pregnancy, they also play important roles in fat storage and loss, muscle growth and bone and tendon/ligament health, so for women who take part in physical activity, consideration of these hormones, their fluctuations and interactions can be important to guide both training and nutrition strategies.


Oestrogen and progesterone work synergistically to illicit many effects on the body. The oestrogens are fundamental for developing female sexual characteristics, including widening of the hips and increase in fatty tissue around the breasts, hips and buttocks during puberty and oestrogen imbalances in terms of both a lack of oestrogen and the creation of too much oestrogen have been associated with health conditions and unwanted increases in body fat due to the finely balanced roles oestrogen plays in the flux of energy in and out of fat cells.


Progesterone, like oestrogen is produced in the ovaries and is the main form of the progestin group of hormones found in the body. The menstrual cycle can be divided into two phases that are separated by ovulation (the release of the egg). These two phases are the follicular phase and the luteal phase. The follicular phase is associated with higher oestrogen levels in comparison to progesterone, and during the luteal phase, progesterone’s release starts after ovulation and concentration levels rise rapidly and continue to be elevated throughout the luteal phase.


Elevation of the progestin’s have been associated with thermogenic effects such as an increase in body temperature and minute ventilation, this is the amount of oxygen the body takes up within a minute. In theory, if we can provide more oxygen to the muscles and remove waste products more effectively, then greater performance or training output can be achieved. Progestin’s are also anabolic in nature, so the luteal phase is seen by some as a time to focus on muscle growth and strength training. It is the elevations, reductions and ratios of these hormones found in the body during different phases of the menstrual cycle that some people have suggested should influence the different nutritional and training requirements that should be tailored to each phase in order to optimise training, fat loss and recovery, although these ideas are at present far from supported by current research with very little evidence supporting these ideas for either endurance or strength training. So at present, training should still be focussed on your specific goals and nutrition tailored to such needs, with no evidence that these should be adjusted depending on the phase of the menstrual cycle aside from the obvious pain and discomfort that will undoubtedly influence training capacity in some women.


Fat usage is largely controlled by activation of two types of adrenergic receptors in the body. Adrenergic receptors work to speed up or slow down fatty acid release from stored body fat, depending on which receptor type is stimulated. Oestrogen activates alpha-adrenergic receptors and this is linked to increased fat storage, whilst progesterone has been shown to activate fat releasing beta-adrenergic receptors and decrease the numbers of alpha-adrenergic receptors. This is why elevated oestrogen, especially combined with low progesterone, can lead to fat storage associated with ‘oestrogen dominance’.


Therefore, progesterone and oestrogen both influence fat storage around the waist and these interact with other hormones that can profoundly impact on their ability to regulate fat storage. In particular, chronically high levels of cortisol can interrupt progesterone’s effects on maintaining or reducing body fat, meaning management of environmental, nutritional and exercise stress becomes an important consideration. When progesterone is in balance with oestrogen and other hormones, it aids fat loss for women and has muscle building benefits.


Oestrogen is also important for women as it supports insulin response and insulin sensitivity… And if you’ve read our other work on the importance of insulin sensitivity part one and two, you will see just how important this is. Regular exercise is perhaps one of the most important aspects of female health. It improves insulin sensitivity, reduces stress and increases progesterone, growth hormone and helps balance progesterone and oestrogen ratios.


All of these factors should be considered in females who are looking to build muscle and/or reduce body fat levels. Perhaps the greatest benefit of exercise and proper nutrition comes after the menopause when these hormones are not present in sufficient amounts to protect bone mineral density, which can lead to an increased risk of breaks and fractures, which is a leading cause of loss of quality of life in elderly populations. Exercise, especially when you are producing these hormones, can build up bone density and offer long term protective effects.


On a final, and I feel important note, prolonged periods of insufficient nutrient intake can lead to disruptions of the menstrual cycle and although low body fat levels might be desirable for a competition or photoshoot, if these are forced too low for too long then this can disrupt normal menstrual and hormonal function and have long term health implications.