Hormones and Neurotransmitters: The Differences and Curious Similarities

Alpana and Murari Chaudhuri wrote . . . . . . . . .

Overview

Neurotransmitters and hormones are two different types of chemicals that carry signals from one part of the body to another. Both chemicals play an important part in the body’s physiology. They control a variety of physical and psychological functions, including our mood, our eating patterns, our ability to learn, and our sleep cycles.

The Differences

Hormones and neurotransmitters are different chemical messengers, the former produced by the endocrine glands and the latter by the nervous system.

Hormones are usually secreted from the endocrine system and released into the bloodstream, but they act on distant target cells. Some hormones, like melatonin and cortisol, are actually produced in the brain, released in the blood, and affect other parts of the body.

On the other hand, neurotransmitters are released from the presynaptic nerve terminal in the brain. They move across the synaptic cleft, a small space between two adjacent neurons, and move to the next neuron (known as a postsynaptic neuron). There they bind to specific receptors, causing changes in the electrical properties of target cells, which can cause various postsynaptic effects. Neurotransmitters work locally and their actions are very fast.

Both hormones and neurotransmitters influence our thoughts and motivations, as well as our ability to learn and concentrate. However, neurotransmitters’ actions are short-lived while hormones act for longer periods of time. Furthermore, neurotransmitters can affect both voluntary actions (eating, bathing, walking) and involuntary actions (breathing, blinking). Hormones in the endocrine system always work involuntarily.

Curious Similarities

Research in the last couple of years has demonstrated that some hormones, work like neurotransmitters independently of their classical hormone actions. The most well-studied hormones are progesterone and estrogen, which are known as steroid hormones.

Steroid hormones are typically synthesized in the endocrine gland and bind to a receptor that then binds to a specific DNA sequence, affecting gene transcription. This process is a lengthy one, which means that steroid hormones work for a prolonged period of time.

However, Progesterone and estrogen are also synthesized in the neuronal circuit, specifically in the presynaptic terminal. They then bind to the membrane and intracellular receptors followed by neurotransmitter-like action, which is very fast and short-lived. These neurotransmitters-like steroids have multiple receptors. The steroid-receptor specific functions are not yet clearly understood.

Some well-studied neuroreceptors, like dopamine and serotonin are known to possess hormonal functions. Dopamine is a neurohormone released from the hypothalamus; its main function is to block the release of prolactin, another hormone, from the pituitary gland. As a neurotransmitter released from the central nervous system, it also has many functions including roles in cognition and motor activity.

Adrenaline and noradrenaline are two molecules that differ by one carbon atom. Adrenaline, which is produced by the adrenal gland, acts as a hormone. On the other hand, noradrenaline acts as a neurotransmitter in the central nervous system.

This is just a piece of a growing body of research suggesting that many hormones work as neurotransmitters and vice-versa. The next area of research here is to determine the receptor-specificity of these molecules to understand how their function may change depending on the receptor and mode of binding.

Source: The Biochemists

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Study: Just 20 Minutes of Contact with Nature Will Lower Stress Hormone Levels

Taking at least twenty minutes out of your day to stroll or sit in a place that makes you feel in contact with nature will significantly lower your stress hormone levels. That’s the finding of a study that has established for the first time the most effective dose of an urban nature experience. Healthcare practitioners can use this discovery, published in Frontiers in Psychology, to prescribe ‘nature-pills’ in the knowledge that they have a real measurable effect.

“We know that spending time in nature reduces stress, but until now it was unclear how much is enough, how often to do it, or even what kind of nature experience will benefit us,” says Dr. MaryCarol Hunter, an Associate Professor at the University of Michigan and lead author of this research. “Our study shows that for the greatest payoff, in terms of efficiently lowering levels of the stress hormone cortisol, you should spend 20 to 30 minutes sitting or walking in a place that provides you with a sense of nature.”

A free and natural stress-relieving remedy

Nature pills could be a low-cost solution to reduce the negative health impacts stemming from growing urbanization and indoor lifestyles dominated by screen viewing. To assist healthcare practitioners looking for evidence-based guidelines on what exactly to dispense, Hunter and her colleagues designed an experiment that would give a realistic estimate of an effective dose.

Over an 8-week period, participants were asked to take a nature pill with a duration of 10 minutes or more, at least 3 times a week. Levels of cortisol, a stress hormone, were measured from saliva samples taken before and after a nature pill, once every two weeks.

“Participants were free to choose the time of day, duration, and the place of their nature experience, which was defined as anywhere outside that in the opinion of the participant, made them feel like they’ve interacted with nature. There were a few constraints to minimize factors known to influence stress: take the nature pill in daylight, no aerobic exercise, and avoid the use of social media, internet, phone calls, conversations and reading,” Hunter explains.

She continues, “Building personal flexibility into the experiment, allowed us to identify the optimal duration of a nature pill, no matter when or where it is taken, and under the normal circumstances of modern life, with its unpredictability and hectic scheduling.”

To make allowances for busy lifestyles, while also providing meaningful results, the experimental design was novel in other aspects too.

“We accommodated day to day differences in a participant’s stress status by collecting four snapshots of cortisol change due to a nature pill,” says Hunter. “It also allowed us to identify and account for the impact of the ongoing, natural drop in cortisol level as the day goes on, making the estimate of effective duration more reliable.”

Nature will nurture

The data revealed that just a twenty-minute nature experience was enough to significantly reduce cortisol levels. But if you spent a little more time immersed in a nature experience, 20 to 30 minutes sitting or walking, cortisol levels dropped at their greatest rate. After that, additional de-stressing benefits continue to add up but at a slower rate.

“Healthcare practitioners can use our results as an evidence-based rule of thumb on what to put in a nature-pill prescription,” says Hunter. “It provides the first estimates of how nature experiences impact stress levels in the context of normal daily life. It breaks new ground by addressing some of the complexities of measuring an effective nature dose.”

Hunter hopes this study will form the basis of further research in this area.

“Our experimental approach can be used as a tool to assess how age, gender, seasonality, physical ability and culture influences the effectiveness of nature experiences on well-being. This will allow customized nature pill prescriptions, as well as a deeper insight on how to design cities and wellbeing programs for the public.”

Source: Science Daily

Stress in Childhood and Adulthood Have Combined Impact on Hormones and Health

Adults who report high levels of stress and who also had stressful childhoods are most likely to show hormone patterns associated with negative health outcomes, according to findings published in Psychological Science, a journal of the Association for Psychological Science.

One of the ways that our brain responds to daily stressors is by releasing a hormone called cortisol — typically, our cortisol levels peak in the morning and gradually decline throughout the day. But sometimes this system can become dysregulated, resulting in a flatter cortisol pattern that is associated with negative health outcomes.

“What we find is that the amount of a person’s exposure to early life stress plays an important role in the development of unhealthy patterns of cortisol release. However, this is only true if individuals also are experiencing higher levels of current stress, indicating that the combination of higher early life stress and higher current life stress leads to the most unhealthy cortisol profiles,” says psychological scientist Ethan Young, a researcher at the University of Minnesota.

For the study, Young and colleagues examined data from 90 individuals who were part of a high-risk birth cohort participating in the Minnesota Longitudinal Study of Risk and Adaptation.

The researchers specifically wanted to understand how stressful events affect the brain’s stress-response system later in life. Is it the total amount of stress experienced across the lifespan that matters? Or does exposure to stress during sensitive periods of development, specifically in early childhood, have the biggest impact?

Young and colleagues wanted to investigate a third possibility: Early childhood stress makes our stress-response system more sensitive to stressors that emerge later in life.

The researchers assessed data from the Life Events Schedule (LES), which surveys individuals’ stressful life events, including financial trouble, relationship problems, and physical danger and mortality. Trained coders rate the level of disruption of each event on a scale from 0 to 3 to create an overall score for that measurement period. The participants’ mothers completed the interview when the participants were 12, 18, 30, 42, 48, 54, and 64 months old; when they were in Grades 1, 2, 3, and 6; and when they were 16 and 17 years old. The participants completed the LES themselves when they were 23, 26, 28, 32, 34, and 37 years old.

The researchers grouped participants’ LES scores into specific periods: early childhood (1-5 years), middle childhood (Grades 1-6), adolescence (16 and 17 years), early adulthood (23-34 years), and current (37 years).

At age 37, the participants also provided daily cortisol data over a 2-day period. They collected a saliva sample immediately when they woke up and again 30 minutes and 1 hour later; they also took samples in the afternoon and before going to bed. They sent the saliva samples to a lab for cortisol-level testing.

The researchers found that neither total life stress nor early childhood stress predicted cortisol level patterns at age 37. Rather, cortisol patterns depended on both early childhood stress and stress at age 37. Participants who experienced relatively low levels of stress in early childhood showed relatively similar cortisol patterns regardless of their stress level in adulthood. On the other hand, participants who had been exposed to relatively high levels of early childhood stress showed flatter daily cortisol patterns, but only if they also reported high levels of stress as adults.

The researchers also investigated whether life stress in middle childhood, adolescence, and early adulthood were associated with adult cortisol patterns, and found no meaningful relationships.

These findings suggest that early childhood may be a particularly sensitive time in which stressful life events — such as those related to trauma or poverty — can calibrate the brain’s stress-response system, with health consequences that last into adulthood.

Young and colleagues note that cortisol is one part of the human stress-response system, and they hope to investigate how other components, such as the microbiome in our gut, also play a role in long-term health outcomes.

Source: Association for Psychological Science

Insulin Resistance Causes and Symptoms

Sari Harrar wrote . . . . . . . . .

One in three Americans—including half of those age 60 and older — have a silent blood sugar problem known as insulin resistance. Insulin resistance increases the risk for prediabetes, type 2 diabetes and a host of other serious health problems, including heart attacks, strokes and cancer.

What is Insulin Resistance?

Insulin resistance is when cells in your muscles, body fat and liver start resisting or ignoring the signal that the hormone insulin is trying to send out—which is to grab glucose out of the bloodstream and put it into our cells. Glucose, also known as blood sugar, is the body’s main source of fuel. We get glucose from grains, fruit, vegetables, dairy products, and drinks that bring break down into carbohydrates.

How Insulin Resistance Develops

While genetics, aging and ethnicity play roles in developing insulin sensitivity, the driving forces behind insulin resistance include excess body weight, too much belly fat, a lack of exercise, smoking, and even skimping on sleep.

As insulin resistance develops, your body fights back by producing more insulin. Over months and years, the beta cells in your pancreas that are working so hard to make insulin get worn out and can no longer keep pace with the demand for more and more insulin. Then – years after insulin resistance silently began – your blood sugar may begin to rise and you may develop prediabetes or type 2 diabetes. You may also develop non-alcoholic fatty liver disease (NAFLD), a growing problem associated with insulin resistance that boosts your risk for liver damage and heart disease.

Signs and Symptoms of Insulin Resistance

Insulin resistance is usually triggered by a combination of factors linked to weight, age, genetics, being sedentary and smoking.

A large waist. Experts say the best way to tell whether you’re at risk for insulin resistance involves a tape measure and moment of truth in front of the bathroom mirror. A waist that measures 35 inches or more for women, 40 or more for men (31.5 inches for women and 35.5 inches for men if you’re of Southeast Asian, Chinese or Japanese descent) increases the odds of insulin resistance and metabolic syndrome, which is also linked to insulin resistance.

You have additional signs of metabolic syndrome. According to the National Institutes of Health, in addition to a large waist, if you have three or more of the following, you likely have metabolic syndrome, which creates insulin resistance.

  • High triglycerides. Levels of 150 or higher, or taking medication to treat high levels of these blood fats.
  • Low HDLs. Low-density lipoprotein levels below 50 for women and 40 for men – or taking medication to raise low high-density lipoprotein (HDL) levels.
  • High blood pressure. Readings of 130/85 mmHg or higher, or taking medication to control high blood pressure
  • High blood sugar. Levels of 100-125 mg/dl (the prediabetes range) or over 125 (diabetes).
  • High fasting blood sugar (or you’re on medicine to treat high blood sugar). Mildly high blood sugar may be an early sign of diabetes.

You develop dark skin patches. If insulin resistance is severe, you may have visible skin changes. These include patches of darkened skin on the back of your neck or on your elbows, knees, knuckles or armpits. This discoloration is called acanthosis nigricans.

Health Conditions Related to Insulin Resistance

An estimated 87 million American adults have prediabetes; 30-50% will go on to develop full-blown type 2 diabetes. In addition, up to 80% of people with type 2 diabetes have NAFLD. But those aren’t the only threats posed by insulin resistance.

Thanks to years of high insulin levels followed by an onslaught of cell-damaging high blood sugar, people with insulin resistance, prediabetes and type 2 diabetes are at high risk for cardiovascular disease. Insulin resistance doubles your risk for heart attack and stroke – and triples the odds that your heart attack or ‘brain attack’ will be deadly, according to the International Diabetes Federation.

Meanwhile, insulin resistance and metabolic syndrome are also linked with higher risk for cancers of the bladder, breast, colon, cervix, pancreas, prostate and uterus. The connection: High insulin levels early in insulin resistance seem to fuel the growth of tumors and to suppress the body’s ability to protect itself by killing off malignant cells.

How You Can Prevent or Reverse Insulin Resistance

Losing weight, getting regular exercise and not skimping on sleep can all help improve your insulin sensitivity. Don’t rely on dieting or exercise alone: in one fascinating University of New Mexico School of Medicine study, published in the International Journal of Obesity, overweight people who lost 10% of their weight through diet plus exercise saw insulin sensitivity improve by an impressive 80%. Those who lost the same amount of weight through diet alone got a 38% increase. And those who simply got more exercise, but didn’t lose much weight, saw almost no shift in their level of insulin resistance.

Turn in on time, too. In a study presented at the 2015 meeting of the Obesity Society, researchers found that just one night of sleep deprivation boosted insulin resistance as much as eating high-fat foods for six months.

Source: Endocrine Web

Hormones: Insulin

What is Insulin?

Insulin is a hormone made by an organ located behind the stomach called the pancreas. There are specialised areas within the pancreas called islets of Langerhans (the term insulin comes from the Latin insula that means island). The islets of Langerhans are made up of different type of cells that make hormones, the commonest ones are the beta cells, which produce insulin.

Insulin is then released from the pancreas into the bloodstream so that it can reach different parts of the body. Insulin has many effects but mainly it controls how the body uses carbohydrates found in certain types of food. Carbohydrates are broken down by the human body to produce a type of sugar called glucose. Glucose is the main energy source used by cells. Insulin allows cells in the muscles, liver and fat (adipose tissue) to take up this glucose and use it as a source of energy so they can function properly. Without insulin, cells are unable to use glucose as fuel and they will start malfunctioning. Extra glucose that is not used by the cells will be converted and stored as fat so it can be used to provide energy when glucose levels are too low. In addition, insulin has several other metabolic effects (such as stopping the breakdown of protein and fat).

How is insulin controlled?

The main actions that insulin has are to allow glucose to enter cells to be used as energy and to maintain the amount of glucose found in the bloodstream within normal levels. The release of insulin is tightly regulated in healthy people in order to balance food intake and the metabolic needs of the body. This is a complex process and other hormones found in the gut and pancreas also contribute to this blood glucose regulation. When we eat food, glucose is absorbed from our gut into the bloodstream, raising blood glucose levels. This rise in blood glucose causes insulin to be released from the pancreas so glucose can move inside the cells and be used. As glucose moves inside the cells, the amount of glucose in the bloodstream returns to normal and insulin release slows down. Proteins in food and other hormones produced by the gut in response to food also stimulate insulin release. Hormones released in times of acute stress, such as adrenaline, stop the release of insulin, leading to higher blood glucose levels to help cope with the stressful event.

Insulin works in tandem with glucagon, another hormone produced by the pancreas. While insulin’s role is to lower blood sugar levels if needed, glucagon’s role is to raise blood sugar levels if they fall too low. Using this system, the body ensures that the blood glucose levels remain within set limits, which allows the body to function properly.

What happens if I have too much insulin?

If a person accidentally injects more insulin than required, e.g. because they expend more energy or eat less food than they anticipated, cells will take in too much glucose from the blood. This leads to abnormally low blood glucose levels (called hypoglycaemia). The body reacts to hypoglycaemia by releasing stored glucose from the liver in an attempt to bring the levels back to normal. Low glucose levels in the blood can make a person feel ill.

The body mounts an initial ‘fight back’ response to hypoglycaemia through a specialised set of of nerves called the sympathetic nervous system. This causes palpitations, sweating, hunger, anxiety, tremor and pale complexion that usually warn the person about the low blood glucose level so this can be treated. However, if the initial blood glucose level is too low or if it is not treated promptly and continues to drop, the brain will be affected too because it depends almost entirely on glucose as a source of energy to function properly. This can cause dizziness, confusion, fits and even coma in severe cases.

Some drugs used for people with type 2 diabetes, including sulphonylureas (e.g. gliclazide) and meglitinides (e.g. repaglinide), can also stimulate insulin production within the body and can also cause hypoglycaemia. The body responds in the same way as if excess insulin has been given by injection.

Furthermore, there is a rare tumour called an insulinoma that occurs with an incidence of 1-4 per million population. It is a tumour of the beta cells in the pancreas. Patients with this type of tumour present with symptoms of hypoglycaemia.

What happens if I have too little insulin?

People with diabetes have problems either making insulin, how that insulin works or both. The main two types of diabetes are type 1 and type 2 diabetes, although there are other more uncommon types.

People with type 1 diabetes produce very little or no insulin at all. This condition is caused when the beta cells that make insulin have been destroyed by antibodies (these are usually substances released by the body to fight against infections), hence they are unable to produce insulin. With too little insulin, the body can no longer move glucose from the blood into the cells, causing high blood glucose levels. If the glucose level is high enough, excess glucose spills into the urine. This drags extra water into the urine causing more frequent urination and thirst. This leads to dehydration, which can cause confusion. In addition, with too little insulin, the cells cannot take in glucose for energy and other sources of energy (such as fat and muscle) are needed to provide this energy. This makes the body tired and can cause weight loss. If this continues, patients can become very ill. This is because the body attempts to make new energy from fat and causes acids to be produced as waste products. Ultimately, this can lead to coma and death if medical attention is not sought. People with type 1 diabetes will need to inject insulin in order to survive.

Type 2 diabetes can be caused by two main factors and its severity will depend on how advanced it is. Firstly, the patient’s beta cells may have problems manufacturing insulin, so although some insulin is produced, it is not enough for the body’s needs. Secondly, the available insulin doesn’t work properly because the areas in the cell where insulin acts, called insulin receptors, become insensitive and stop responding to the insulin in the bloodstream. These receptors appear to malfunction more in people who carry excessive amount of weight. Some people with type 2 diabetes might initially experience very few symptoms and the raised blood glucose is only picked up when a routine blood test is arranged for another reason; other people might experience symptoms similar to those seen in patients with type 1 diabetes (thirst, frequent urination, dehydration, hunger, fatigue and weight loss). Some patients with type 2 diabetes can control their symptoms by improving their diet and/or losing weight, some will need tablets, and others will need to inject insulin to improve blood glucose levels.

Source: Society for Endocrinology


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Insulin and Glucose Regulation . . . . .