Hormones are chemical messengers.
Hormones cause responses in target cells.
Hormones are secreted by endocrine glands.
Endocrine glands secrete hormones into the blood.
Hormones are then transported in the blood to target cells.
Hormones bind to complementary and specific receptors on target cells.
When a hormone binds to a receptor, a response is triggered in the cell.
Exocrine glands also exist. Exocrine glands secrete products (like enzymes) into ducts.
There are two types of hormone:
Steroid hormones are lipid-based, so can cross the phospholipid bilayer.
Steroid hormones then bind with receptors in the cytoplasm.
They form steroid-receptor complexes which bind to specific DNA sequences, affecting the transcription rate of a particular gene.
They cause the production of a protein or enzyme during translation, which affects a cell's behaviour.
Peptide hormones are peptide-based and hydrophilic, so they can't cross a membrane's phospholipid bilayer.
Peptide hormones bind to receptors on the cell surface.
This activates a G protein.
The activated G protein activates an effector molecule (adenyl cyclase).
Adenyl cyclase converts ATP to cAMP.
cAMP becomes a second messenger inside the cell.
cAMP activates intracellular enzymes which affect the cell's behaviour.
The pancreas is a leaf-shaped organ found near the stomach.
It has both endocrine and exocrine functions.
Its exocrine tissue are called acini cells.
Acini cells secrete digestive enzymes into the pancreatic duct.
Its endocrine tissue is called the islets of Langerhans which contain alpha and beta cells.
Alpha cells produce glucagon.
Beta cells produce insulin.
Glucagon and insulin are both peptide hormones.
Glucagon stimulates glycogenolysis.
Glycogenolysis is the breakdown of stored glycogen to glucose which is released in the blood to raise sugar levels.
Insulin stimulates glycogenesis.
Glycogenesis is the conversion of glucose into glycogen to be stored.
Insulin also stimulates the uptake of glucose into cells.
Here's how insulin is secreted from beta cells in the pancreas:
Diabetes is a condition in which there is a lack of insulin, or a reduced sensitivity to insulin, meaning the body cannot properly control blood glucose levels.
There are two main types of diabetes: Type 1 diabetes and Type 2 diabetes.
Type 1 Diabetes
Type 1 diabetes is an autoimmune condition.
The immune system attacks and destroys the beta cells in the islets of Langerhans.
As a result, the pancreas cannot produce insulin.
Because no insulin is produced, blood-glucose levels rise and remain high.
Type 1 diabetes usually develops in childhood or adolescence, but can occur at any age.
People with Type 1 diabetes require insulin injections, or an insulin pump, to control their blood-glucose levels.
They must carefully monitor their blood-glucose levels to avoid hyperglycaemia and hypoglycaemia.
Type 2 Diabetes
Type 2 diabetes is usually caused by lifestyle factors, such as a high-sugar diet, lack of exercise, obesity, or genetic predisposition.
In Type 2 diabetes, beta cells still produce insulin, but target cells become less responsive to it.
This is known as insulin resistance.
Because cells do not respond properly to insulin, blood-glucose levels rise.
Type 2 diabetes typically develops later in life, but can occur in younger people due to poor lifestyle choices.
It is often managed through diet and exercise, and sometimes medication to improve insulin sensitivity.
Symptoms of Diabetes
Both types of diabetes cause similar symptoms, including:
Treating Diabetes
Type 1 diabetes requires insulin therapy to replace the insulin that the body cannot produce.
Insulin therapy can be delivered by injections or insulin pumps.
Type 1 diabetics must also carefully monitor their blood-glucose levels.
Type 2 diabetes can often be managed through lifestyle changes, such as eating a balanced diet, increasing exercise, and losing weight.
If lifestyle changes are not enough, medication may be needed to increase the effectiveness of insulin or to reduce blood-glucose levels.
Stem Cell Treatment for Diabetes
Scientists are researching the use of stem cells to treat diabetes.
Stem cells could be used to grow new beta cells to replace the destroyed or damaged ones.
This could allow people with Type 1 diabetes to begin producing insulin naturally again.
This treatment is still experimental, but researchers believe it may offer a cure for diabetes in the future.
The Importance of Blood-Glucose Control
Keeping blood-glucose levels within a normal range prevents both hyperglycaemia and hypoglycaemia.
Consistently high blood-glucose levels can cause long-term damage, including nerve damage, kidney damage, and problems with eyesight.
Gestational Diabetes
Gestational diabetes is a form of diabetes that develops during pregnancy.
It occurs when a pregnant woman's body becomes less responsive to insulin.
This insulin resistance is caused by hormones produced by the placenta, which can reduce the effectiveness of insulin.
As a result, blood-glucose levels can rise, similar to Type 2 diabetes.
Gestational diabetes usually develops in the later stages of pregnancy and often disappears after birth.
However, women who have had gestational diabetes have a higher risk of developing Type 2 diabetes later in life.
Gestational diabetes is managed through careful monitoring of blood-glucose levels, dietary changes, and sometimes insulin therapy if required.
It is important to control blood-glucose levels during pregnancy to protect the health of both the mother and the baby.