Disorders of the Pituitary Gland

Endocrine and Metabolic Disorders

• Disorders include those of the pituitary, thyroid, adrenal cortex, and diabetes mellitus.

The Endocrine System

• The endocrine system monitors and responds to changes in homeostasis.
• Endocrine tissues create and release hormones transported in the blood to target cells.

Hormone Response

• Hormones respond to cellular environment changes, including chemical factors (like blood glucose or calcium), other hormones, and neural stimuli.
• Positive feedback increases hormone synthesis and secretion.
• Negative feedback decreases hormone synthesis and secretion.

Endocrine Disorders

• Disorders are categorized by target organ, direction of change (hyper/hypo function), and the underlying mechanism.
• Primary disorders affect the endocrine organ.
• Secondary disorders affect the signaling molecules regulating hormone secretion.

Disorders of the Pituitary Gland

• The hypothalamus senses changes in the cellular environment and releases hormones to regulate the pituitary release of hormones.
• The hypothalamus secretes releasing and inhibiting hormones, triggering the release of hormones into the bloodstream.
• Hyperfunction can cause syndrome of inappropriate antidiuretic hormone secretion (SIADH) with excess ADH.
• Hypofunction can cause diabetes insipidus with insufficient ADH.
• Pituitary adenomas are benign tumors in the anterior pituitary leading to hyperpituitarism.

Disorders of the Adrenal Cortex

• The adrenal glands consist of an inner adrenal medulla and outer adrenal cortex.
• The adrenal cortex has three zones responsible for making steroid hormones: zona glomerulosa produces mineralocorticoids (aldosterone), zona fasciculata makes glucocorticoids (cortisol), and zona reticularis produces sex hormones.
• Cortisol, a stress hormone is produced in response to chemical, neural, and endocrine signals.
• Hyperfunction (Cushing's syndrome) leads to high cortisol levels causing various symptoms. The cause can be a tumor.
• Hypofunction (Addison's disease) results in low cortisol levels leading to different symptoms.

Thyroid Gland Disorders

• The thyroid gland produces thyroid hormones (T3 and T4).
• The thyroid contains follicular cells (that produce thyroid hormones) and C cells (that produce calcitonin).
• Hypothyroidism is characterized by low T3 and T4 levels and high TSH levels.
• Hyperthyroidism is characterized by high T3 and T4 levels and low TSH levels. Common causes include Graves' disease, toxic multinodular goiter, and solitary toxic nodule.

Diabetes Mellitus

• Diabetes mellitus is a group of metabolic disorders characterized by chronic hyperglycemia.
• The pancreas produces the hormones insulin and glucagon.
• Type 1 diabetes results from beta cell destruction (usually autoimmune).
• Type 2 diabetes is caused by insulin resistance and impaired insulin secretion.

Liver and Diabetes

• The liver stores glucose as glycogen and releases glucose when blood glucose is low through gluconeogenesis.
• In diabetes the liver does not respond to insulin and there is excess glucose in the blood.

Metabolic Syndrome

• The presence of multiple risk factors including central obesity, high triglycerides, low HDL, high blood pressure, and high fasting plasma glucose.
• These factors can increase the risk of type 2 diabetes and cardiovascular disease.

Complications of Diabetes Mellitus

• Acute complications may include hypoglycemia, diabetic ketoacidosis.
• Chronic complications include macrovascular disease (cardiovascular disease, stroke, peripheral artery disease) and microvascular disease (retinopathy, nephropathy, neuropathy)

Oxidative Stress and Glycation

• Chronic hyperglycemia results in oxidative stress (reactive oxygen species) and glycation (binding of glucose to proteins).
• These processes damage various tissues.

Polyol Pathway and Diabetic Complications

• A biochemical pathway that results in increased sorbitol levels in cells (especially in eyes, nerves, and kidneys).
• This can damage cells and lead to complications like neuropathy and retinopathy.

Nephropathies

• Progressive kidney changes with glomerular damages (intercapillary glomerulosclerosis)
• Leading to increased risk of kidney disease.

Microvascular and Macrovascular Disease

• Changes in small blood vessels and lead to complications like retinopathy (eyes), nephropathy (kidneys), and neuropathy (nerves).

Exercise and Diabetes

• Aerobic and resistance training are important lifestyle interventions for managing diabetes.
• Both types of training can improve glucose use in skeletal muscles.