Endocrine Glands and Thyroid Gland Overview

The thyroid gland regulates metabolic rate and blood calcium levels.

Thyroid hormones (T3 and T4) control metabolic rate and heat production.

T3 has 3 iodine atoms, and T4 has 4 iodine atoms. They both regulate metabolic processes but differ in function to some extent

T3 enters cells and interacts with intracellular receptors, influencing gene expression and cellular processes.

TH levels are controlled by negative feedback through hormones TRH and TSH, influenced by the hypothalamus.

The hypothalamus ultimately controls the metabolic rate via hormones that regulate the release of thyroid hormone

Almost all cells in the body are target cells for thyroid hormones.

Iodine is essential for the production of T3 and T4 hormones by the thyroid gland.

The hypothalamus releases thyroid-releasing hormone (TRH), which stimulates the pituitary gland to release thyroid-stimulating hormone (TSH).

The pituitary gland releases thyroid-stimulating hormone (TSH) in response to TRH from the hypothalamus. TSH acts on the thyroid gland to produce and release thyroid hormones.

The thyroid gland produces and releases thyroid hormones (T3 and T4), which regulate metabolism and energy use in the body.

Hypothyroidism occurs when the thyroid gland doesn't produce enough thyroid hormone. This can be due to issues with the hypothalamus, pituitary gland, or the thyroid itself.

Slow metabolic rate, fatigue, weight gain, cold intolerance are common symptoms of hypothyroidism.

Hyperthyroidism occurs when the thyroid gland produces too much thyroid hormone. This can be due to issues with the hypothalamus, pituitary gland, or the thyroid itself.

Fast metabolic rate, weight loss, increased heart rate, heat intolerance, nervousness are common symptoms of hyperthyroidism.

An autoimmune disorder where the immune system attacks the thyroid gland, leading to hypothyroidism.

An autoimmune disease causing hyperthyroidism due to antibodies stimulating thyroid hormone production, leading to elevated T3 and T4, and potentially eye problems.

Despite elevated thyroid hormone levels, patients with Graves' disease have low TRH and TSH due to the negative feedback loop.

The outer layer of the adrenal gland produces steroid hormones, including cortisol and sex hormones.

The inner layer of the adrenal gland secretes catecholamines, like epinephrine and norepinephrine, for short-term stress response.

Cortisol helps mobilize nutrients, increase metabolic rate, and suppress non-essential functions in response to stress.

Cortisol levels peak in the morning, influenced by melatonin's decline, preparing the body for activity.

Sustained high cortisol due to chronic stress weakens the immune system, making the body susceptible to infections.

Cortisol breaks down stored carbohydrates, proteins, and fats to provide energy during stress.

Epinephrine (E) and norepinephrine (NE) are hormones released during the 'fight or flight' response. They increase heart rate, respiration, and blood flow to muscles, preparing the body for action.

The sympathetic nervous system is part of the autonomic nervous system. It controls the 'fight or flight' response, preparing the body for stress or danger.

The adrenal medulla is part of the adrenal glands. It releases E and NE into the bloodstream during stress.

The pancreas regulates blood glucose levels by releasing two hormones: glucagon (increases glucose) and insulin (decreases glucose).

Glucagon increases blood glucose levels by converting stored glycogen in the liver into glucose and releasing it into the bloodstream.

Insulin decreases blood glucose levels by inhibiting liver glycogen breakdown, stimulating muscle glucose uptake, and promoting glucose storage in fat cells.

Diabetes is a condition where blood glucose levels are consistently high. It can be caused by insufficient insulin production (Type I) or resistance to insulin's effects (Type II).

Type I diabetes is caused by the body's immune system attacking insulin-producing cells, requiring insulin injections. Type II is caused by insulin resistance.

A chronic condition where the body does not use insulin properly, leading to high blood sugar levels. It develops gradually over years.

Symptoms include increased thirst and hunger, frequent urination, blurred vision, and gradual weight loss.

When diabetes is not managed effectively, high blood sugar levels persist, damaging blood vessels over time.

Long-term complications of uncontrolled diabetes include heart disease, kidney dysfunction, vision loss, and nerve damage.

The testes in males and ovaries in females produce gametes (sperm and egg) and sex hormones (testosterone and estrogen).

The Hypothalamus-Pituitary-Gonad (HPG) axis is a hormonal feedback loop that regulates the production and release of sex hormones.

Testosterone, produced mostly in males, is responsible for sperm production, development of male characteristics, and sex drive.

Estrogen, produced mostly in females, plays a crucial role in the menstrual cycle, development of female characteristics, and pregnancy preparation.