Season 7, Episode 6: The Hormone of Darkness


This week Sue and Meagan are learning all about hormones and how they affect the body, and we might even talk about running!

Listen now: Episode 6: The Hormone of Darkness

Full Show Notes and Resources:

What are hormones?

Cortisolstress hormone that controls your mood, motivation, and fear (known for your body’s fight or flight response), also affects how your body metabolizes food, keeps inflammation down, regulates blood pressure, and controls your body’s sleep/wake cycles, can also boost energy. Cortisol can shut down bodily functions that aren’t necessary when your body is having a crisis of some kind (like shutting down menstruation when energy supply is chronically low). Having too much cortisol in your body for too long can have serious negative effects on the body like anxiety, depression, memory problems, trouble sleeping, and weight gain.

Adrenaline – another stress hormone that is secreted in times of crisis. In response to a threat, adrenaline stimulates the heart to beat faster and harder, increases alertness, increases blood flow to the muscles, and decreases the pain response. Excessively high levels of adrenaline due to stress without actual threat of danger can cause heart damage, insomnia, and a jittery, nervous feeling.

EstrogenEstrogen, or oestrogen, is the primary female sex hormone. It is responsible for the development and regulation of the female reproductive system and secondary sex characteristics. Estrogen also affects metabolism, hunger, and fat storage – which is why changes in estrogen throughout the menstrual cycle can affect your hunger, food intake, and weight gain. Estrogen blunts hunger, so you may feel less hungry at times in your cycle when estrogen is high, like the week before ovulation. It also plays a role in bone formation and muscle protein synthesis.

Progesterone – another female sex hormone that is involved with ovulation and pregnancy. It also affects metabolism, skin health, mood, bone strength, body temperature, inflammation and immune response. Progesterone can have a dramatic effect on mood – when progesterone levels drop before the start of the next menstrual cycle, that is when many women experience sharp changes in mood and heightened irritability (one known characteristic of PMS). Progesterone increases hunger – watch out for hunger when progesterone peaks the week after ovulation.

Testosteronethe main male sex hormone that is also present in women. It is an anabolic steroid – which means it promotes muscle growth. Testosterone usually stays pretty low in women, but we do get a small surge in testosterone around the middle of our cycle. Testosterone enhances libido, so that is something else you might notice in the days around ovulation.

Growth Hormonestimulates growth, cell reproduction, and cell regeneration in humans – because of its ability to promote muscle growth and fat loss, it is used exogenously by bodybuilders, but it is a hormone that all humans produce naturally. Growth hormone is secreted in pulses throughout the day – with a big surge of it coming just before you wake up in the morning. Fasting and vigorous exercise both increase growth hormone, while eating food decreases it.

Erythropoietin (EPO)is an essential hormone for red blood cell production and has been shown to dramatically improve athletic cardiovascular performance. EPO doping has been used by endurance athletes to boost performance illegally, but training at altitude can have similar effects on the body because the lower oxygen levels at altitude can boost natural EPO and red blood cell production.

Insulinregulates blood sugar levels in the body. When you eat food, insulin is secreted to promote the storage of glucose in your liver, muscles, and fat. The glucose goes to the liver first and is stored as glycogen, and once that’s filled, goes to the muscles and again stored as glycogen, and any remaining glucose is stored in the fat cells as fat. Carbohydrates, protein, and fat all raise insulin levels in the blood, but to varying degrees – carbohydrates increase insulin the most, and fat increases insulin the least.

Glucagon the fat-burning hormone. When insulin levels are low, glucagon increases and stored energy (in the form of fat and glycogen) is used to fuel the body. Fasting increases glucagon, and eating suppresses it. You can’t burn your fat for fuel if your insulin is always high, which is why people who are insulin-resistant – like those with diabetes – have a hard time losing bodyfat.

Ghrelin – called the hunger hormone because of its role in regulation of appetite. When ghrelin is high, appetite increases, as does food intake.

Leptin the satiety hormone, when ghrelin is high, leptin is low and vice-versa. When leptin increases, the desire to eat decreases. People who are leptin-resistant (usually obese people) have difficulty feeling “full” or satisfied after eating, despite high levels of leptin (I think I had some degree of leptin-resistance)

Melatonin – a hormone that regulates sleep and wakefulness. Melatonin is involved in the synchronization of the circadian rhythms including sleep-wake timing, blood pressure regulation, and seasonal reproduction. Known as “the hormone of darkness”, the onset of melatonin at dusk promotes activity in nocturnal (night-active) animals and sleep in diurnal ones including humans. This is why it’s recommended to sleep in a darkened room (the absence of light helps to promote release of melatonin). During the night, melatonin regulates leptin, lowering its levels.

Vitamin Dknown as a vitamin, but it is a hormone the kidneys produce that controls blood calcium concentration and impacts the immune system. Only a few foods contain vitamin D (such as mushrooms, egg yolk, or fatty fish). The major natural source of the vitamin is synthesis of cholecalciferol in the skin from cholesterol through a chemical reaction that is dependent on sun exposure. Synthesis of vitamin D in nature is dependent on the presence of UV radiation and subsequent activation in liver and in kidney. Vitamin D has a significant role in calcium homeostasis and metabolism. Vitamin D is necessary for bone mineralization, which should be important to any athlete (you can’t perform with a broken bone!) Additionally, VItamin D also has been shown to enhance muscle synthesis.

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