As we know from week 5’s word “endocrine system” (i.e.: the system of glands that secrete hormones), hormones control absolutely everything in the body - from our nutrient uptake, to our sleep cycle, to our sex drives! The endocrine / hormone system runs on a negative feedback loop which means that when the blood senses too little of a necessary substance in the blood, it taps the brain to release a hormone to negate the deficiency.
For example, let's use a house and it's thermostat for reference. When the weather is cold, you turn the heater on in an effort to bring the house temperature to a comfortable neutral temperature; when the weather is hot, you most likely turn the AC on in an effort to bring the house temperature to a comfortable neutral one.
This week’s word, “thyroxine” is one of two hormones secreted by the thyroid. The thyroid is a gland located in the lower front the neck. Thyroxine has several roles that include: increase metabolism (i.e.: weight loss / weight gain), glucose energy (i.e.: sugar) use, protein & muscle restoration, body temperature, and develop nervous system. In summary: it regulates the speed with which your body cells work.
Your basal metabolic rate (BMR) is the number of calories your body needs to accomplish its most basic (basal) life-sustaining function. An individual’s BMR is largely determined by body size...and is regulated by the thyroid hormone thyroxine, that works alongside a large squad of other hormones. Patients whose thyroid glands were not working were found to have low BMRs, and those with overactive thyroid glands had high BMRs.
FUN FACT: Osteoporosis = Weak Bones
Osteoporosis, as we learned a few units ago, means low bone mass and strength. The thyroid gland and its hormones, thyroxine (T4) and triiodothyronine (T3) are in charge of ensuring normal skeletal development and bone metabolism and maintenance. So, adequate levels of thyroxine in the blood can prevent weak bones and bone fractures.
Like the house and its thermostat, thyroxine exists on a negative feedback loop; so, when the blood (i.e.: the house) senses too little thyroxine floating around, it taps the brain (i.e.: the thermostat) to open the gates and let the thyroxine do its thang! However, certain imbalances can occur that affect the thyroxine draw bridge.
- Neutral - In a 'neutral' or normal functioning thyroid gland, thyroxine is being adequately produced to keep up with your body's needs (i.e.: digestion, cell growth, etc.)
- Hypothyroidism (under-active thyroid) - not enough thyroxine is produced for the body’s needs (most common).
- cell function: the body cells work slower and more sluggish than normal
- result: slow heart rate, constipation (due to decreased activity of your intestine), depression
- Hyperthyroidism (overactive thyroid) - too much thyroxine is produced for the body’s needs.
- cell function: the body cells work faster than normal
- result: rapid heart rate, diarrhea (due to increased activity of your intestine), tiredness, unintentional weight loss
THYROXINE, THYROID GLAND, AND SALT
Iodine (yes, the same kind of salty substance found in kelp/seaweed/etc.) is the oil of the thyroid gland vehicle. Iodine is necessary to create thyroxine and cannot actually be made in the body, so needs to be consumed via grub! It's important to find the "goldilocks" amount of iodine consumption to avoid hyper and hypo active thyroid. Great natural sources of dietary iodine are eggs, cheese, soy sauce, saltwater fish, kelp and soy milk (source).