Hormonal differences between men and women: how much do they affect metabolism?
Do men and women have different hormones? The immediate answer would be: certainly! The woman has estrogen and progesterone, the man has testosterone. Nothing more wrong. Men and women have the same hormones, but in extremely different quantities for different metabolic needs.
And how do these differences in concentration affect metabolism?
Just think of our ancestors: hunter man who needed ready energy, woman responsible for the management of male cubs and their survival, who therefore needed energy reserves, and we immediately understand that there must have been fundamental aspects of the control of metabolic homeostasis regulated differently between males and females. This sexual asymmetry represented an evolutionary paradigm for women to allow them to resist the loss of energy stores.
Perhaps the most illuminating sex difference in energy metabolism is found at the level of the gametes themselves, the sperm and the ovum.
Males produce small, numerous and highly mobile, but disposable, sperm cells. Conversely, the female produces a small number of large, immobile eggs. While the male only shares his genes during conception, the female, through the fertilized egg, provides not only the genes but also the source of energy and the nutrients contained in the cytosol of the egg for the embryo to develop and thrive . Furthermore, the sexual dimorphism goes deeper with the uniparental inheritance of the last energy-producing cell organelle, the mitochondria .
The female transmits this critical organelle; the male doesn't. Therefore, from the beginning of reproduction, there is an important sexual asymmetry, the fact that the gametes of females transmit all their resources, ie their energy reserves, their cytosol and their mitochondria. It is also noteworthy that female mammals bear the costly burden of gestation and suckling and resist the loss of body energy stores during prolonged periods of food shortages so that offspring are not affected. In contrast, in male mammals, energy storage is less of an evolutionary strategy. They must immediately mobilize energy reserves for intense and short-term muscular activity, related to hunting and protection needs.
It has become increasingly evident that skeletal muscle glucose and lipid metabolism are different in men and women .
Female gender has been suggested to have a favorable effect on glucose homeostasis, and available evidence from studies points to a gender difference in whole-body insulin sensitivity and particularly insulin-stimulated glucose uptake by the body. of the musculoskeletal system . It will be a topic of future discussion whether any increased insulin sensitivity of female skeletal muscle could be related to gender-specific regulation of molecular metabolism.
In particular, the molecular mechanism for the storage and oxidative capacities of glucose and fatty acids in skeletal muscle and its implications for utilization during the metabolic situations of daily living underscore their relevance for substrate choice in the metabolic state. nutrition and fasting, and during periods of physical activity and recovery. Together, the management of carbohydrates and lipids and the regulation of their utilization in skeletal muscle have implications for glucose homeostasis throughout the body in men and women. 17-β estradiol is the most important female sex hormone, and the identification of estradiol receptors in skeletal muscle has opened up a role in the regulation of substrate metabolism. Furthermore, higher levels of circulating adipokines such as adiponectin and leptin in women have clear implications for muscle metabolism.
Accordingly, women are predisposed to obesity and metabolic syndrome.
Women tolerate higher levels of body fat due to less belly fat. However, they are at a higher risk of obesity due to their greater propensity to gain weight . Indeed, the global prevalence of obesity is higher in women than in men on all continents. Interestingly, the prevalence of abdominal obesity has increased more in women than in men in the United States in recent decades. Today, the prevalence of visceral obesity associated with the metabolic syndrome is two to ten times higher in women in many countries around the world. This female predisposition to central adiposity is seen in many races, across all age groups, and in both urban and rural areas.
A woman normally has twice the fat mass of a man... Although she is often as obese as a man or with more fat mass, she dies less often from the metabolic complications of obesity .
These first observations led to establish the well-known propensity of women to store adipose tissue in the subcutaneous areas compared to the preferential deposition of visceral fat in men . These differences may be directly related to the sex-specific role of fat, as subcutaneous adipocytes are more suitable for long-term storage while visceral adipocytes are more metabolically active and sensitive to lipolysis.
Surely in all these balances the predominance of estrogen in women compared to men plays a fundamental role.
The female organism , even from a hormonal point of view, is much more complex than the male one, so much so that most researchers avoid studying female rodents due to the greater complexity of the research plans.