Promotes growth of pubic hair in boys and girls; in adult women, promotes muscle mass, blood cell formation, and supports the libido; in adult men, adrenal androgens are less significant because androgens are released primarily from the gonads
What are the major glucocorticoid hormones and their diabetes connections?
Cortisol, corticosterone, and cortisone are the three most important glucocorticoid hormones in the body.
Cortisol, also called hydrocortisone, is the most abundant glucocorticoid produced, accounting for nearly 95 percent of the activity of the glucocorticoids.
These hormones have many varying effects on the body.
In terms of diabetes, effects include the stimulation of glucose synthesis and glycogen formation, especially within the liver.
They also stimulate the release of fatty acids from adipose tissue, which can be used as an energy source; decrease the effects of physical and emotional stress (such as fright, bleeding, and infection, since the added glucose from the liver gives tissues a ready source of energy); suppress allergic and inflammatory reactions (which is important to a person with diabetes, as inflammation can lead to other problems); and decrease and suppress the activities of white blood cells and other components of the immune system.
The adrenal glands rest on top of the kidneys; they produce hormones that affect such things as blood pressure and the body’s response to stress.
DIABETES AND THE THYROID AND PARATHYROID GLANDS
What is the thyroid?
The thyroid is a butterfly-shaped gland in the neck. It is located just below the projection at the front of the neck (called the Adam’s apple in men) and above the collarbone. Its major task is to regulate metabolism of the heart, liver, muscles, and other organs through the release of two hormones, thyroxine (T4) and triiodothyronine (T3). The gland also is part of a feedback mechanism that includes the pituitary gland (in the brain) and the hypothalamus (an area of the brain).
What are T3, T4, and TSH and their functions in the body?
The thyroid itself has hormones and stimulates others to produce substances within certain areas of the body.
These thyroid hormones have wide-ranging effects in regulating the function of virtually every organ, including how the body uses energy.
Consequently, any changes in the thyroid hormone levels in the blood can affect many areas of the body and cause a wide range of symptoms if they are not balanced.
In general, there is a sequence to the release of thyroid hormones.
First, the thyroid-stimulating hormone (TSH) is produced when the brain’s hypothalamus releases a substance called thyrotropin-releasing hormone (TRH).
The TRH then triggers the pituitary gland to release the TSH.
This release causes the thyroid to produce two hormones, triiodothyronine (T3) and thyroxine (T4), both of which help control the body’s metabolism.
From there, the brain’s pituitary gland keeps track of the thyroid hormone levels in the blood, increasing or decreasing the amount of TSH released to keep the levels balanced.
What are some statistics about people who have a thyroid disorder?
According to several thyroid organizations, millions of people have a thyroid disorder.
Thyroid Federation International estimates that up to 300 million people worldwide have thyroid dysfunction, yet over half are unaware of their condition.
According to the American Thyroid Association, it is thought that around 20 million Americans, or 12 percent of the population, have a thyroid disorder (although some research indicates the number may be as high as 27 million).
Gender-wise, it is estimated that women are five to eight times more likely to have a thyroid disorder than men.
It is often said that thyroid disorders are second only to diabetes as the most common condition that affects the human endocrine system.
What is the most common cause of hypothyroidism?
T he most common cause of hypothyroidism is dietary iodine deficiency, with an estimated 200 million people having the condition (although this number differs by a few tens of thousands depending on the report). In the United States, there is a lower incidence of hypothyroidism because iodine is usually added to salt and foods that contain salt. The most common reason for hypothyroidism in the United States is Hashimoto thyroiditis, an inherited autoimmune condition in which the immune system mistakenly attacks the thyroid and which affects more than 14 million Americans.
Hyperthyroidism can manifest as a goiter (the enlargement of the thyroid), which inhibits the gland’s ability to process iodine.
What are hyperthyroidism and hypothyroidism?
If a person has an underactive thyroid gland, it is called hypothyroidism. (“Underactive” means producing lower amounts of thyroxine than normal; a test would show too much TSH, or thyroid-stimulating hormone).
If a person’s thyroid gland is overactive (producing higher amounts of thyroxine than normal; a test would show too little TSH), it is called hyperthyroidism.
This condition is less common than hypothyroidism.
Neither condition is age related, but the conditions are often dependent on gender.
For example, in the case of hyperthyroidism, it is often nine times more common in women than in men.
Is there a connection between diabetes and thyroid disorders?
Yes, according to several studies, including those from the American Diabetes Association, many people who have diabetes are often affected by a thyroid disorder.
In fact, people with diabetes have an increased risk for thyroid problems.
In the general population, about 6 to 8 percent have some type of thyroid disorder, but this figure increases to 10 percent in people who have diabetes.
There also seems to be an autoimmune connection.
When a person has one autoimmune disorder, such as type 1 diabetes, he or she has an increased risk for developing another such disease.
For example, statistics indicate that around 3 percent of women with type 1 diabetes have some form of autoimmune thyroid disease.
Another example is postpartum thyroiditis, a form of autoimmune thyroid disease that causes thyroid dysfunction within a few months after delivery of a child.
It is three times more common in women with diabetes.
As for type 2 diabetes, although it is not an autoimmune disease, there is an unexplained higher occurrence of thyroid problems, especially hypothyroidism.
Some studies suggest that this may be because type 2 diabetes and thyroid disorders often develop as a person ages.
How are people with diabetes affected if they are hypothyroid or hyperthyroid?
Most studies indicate that, in general, if a person with diabetes has hypothyroidism, then there are few problems with blood glucose control, although the condition can reduce the removal of insulin from the bloodstream in people with type 1 diabetes (requiring that the dose of insulin be lower). If a person with diabetes has hyperthyroidism, he or she may have a more difficult time controlling blood glucose levels and may have to increase the insulin amount, as the condition causes an increase in glucose production in the liver, rapid absorption of glucose through the intestines, and increased insulin resistance. In addition, because diabetes can increase a person’s risk for heart disease, and hyperthyroidism often increases the heart rate, the condition may exacerbate certain heart conditions, such as angina, or interfere with the treatment of a heart condition.
What are the parathyroid glands?
There are four rice-grain-sized parathyroid glands located in the neck right behind the thyroid gland.
Their main task is to keep calcium levels in the blood within a certain range by the release of the parathyroid hormone (PTH).
The hormone not only helps muscles and nerves to work properly, but it is also connected to bone strength.
In addition, if a person’s blood calcium is too high, the parathyroid glands make less PTH, lowering the amount of calcium by filtering it out of the blood in the kidneys.
If the person’s blood calcium is low, the parathyroid glands make PTH, telling the body to increase the amount of the element in the blood.
To do this, the body either absorbs more calcium from food in the intestines or it takes calcium from the bones.
Do people with diabetes have more problems with hyperparathyroidism than other people?
Yes, according to several studies, hyperparathyroidism, or a high level of the parathyroid hormone in the blood (it can contribute to a loss of calcium and thus weaken bones), is more prevalent in people with diabetes than in the general population. In addition, the prevalence of diabetes in patients with hyperparathyroidism is higher than in the general population. Studies have also shown that hyperparathyroidism, whether the person has or doesn’t have diabetes, is almost three times more common in females than males and nearly seven times more common in postmenopausal women than in younger women.
DIABETES, HORMONES, AND THE PANCREAS
Where is the pancreas located?
The pancreas (from the Greek, meaning “all flesh”) is located in what is called the abdominopelvic cavity, the area between and behind the stomach and the small intestine, and below the liver. It is an elongated organ that measures about 6 inches (12 to 15 centimeters) long.
Why is the pancreas often called a “mixed gland”?
The pancreas is often called a “mixed gland” because it has both endocrine and exocrine functions.
As an endocrine gland, it secretes hormones into the bloodstream, including insulin and glucagon for blood glucose regulation.
But only 1 percent of the weight of the pancreas serves as an endocrine gland.
The remaining 99 percent has exocrine functions, especially in its relation to the body’s digestive system. (For more about the pancreas, including its functions as an exocrine gland, see the chapter “How Diabetes Affects the Digestive System.”)
The pancreas is located behind the stomach.
What are the pancreatic cells called the islets of Langerhans?
A cluster of cells in the pancreas is called the pancreatic islets (islets of Langerhans). They are also the cells that secrete hormones associated with blood glucose levels. In most adults, there can be between 200,000 and 2 million pancreatic islets scattered throughout the pancreas.
How many different types of cells are found in the islets of Langerhans?
The types of cells in each of the islets of Langerhans include the alpha, beta, delta, and F cells. The two most important types of cells, especially in terms of diabetes, are the alpha cells that produce glucagon for the body and the beta cells that produce insulin (for more about using islets in the future, especially to help curb type 2 diabetes, see the chapter “The Future and Diabetes”).
Why are alpha and beta cells in the pancreas so important to a person with, or without, diabetes?
The pancreas contains two types of cells that help with insulin stability: alpha and beta cells.
Within the islets of Langerhans, the beta cells secrete insulin in response to increased blood glucose levels.
This secretion stimulates the cells to take up glucose, providing energy to the body.
The alpha cells secrete the hormone glucagon in response to a decrease in blood glucose levels, with the hormone binding to glucagon receptors in the liver.
This secretion helps stimulate the breakdown of glycogen and release glucose into the bloodstream. (There are also other cell types in islets, including those that secrete the hormones somatostatin, ghrelin, and pancreatic polypeptide Y, but the alpha and beta cells are the most important to controlling the blood glucose levels in the body.)
The islets of Langerhans contain three types of cells that secrete insulin: alpha, beta, and delta cells.