Endocrine Glands: Hormones, Functions, Releasing Sites & Disorders
The endocrine system plays a vital role in maintaining balance in the body by releasing hormones directly into the bloodstream. These hormones act as chemical messengers to control growth, metabolism, mood, sexual development, reproduction, and homeostasis.
Unlike exocrine glands (like salivary or sweat glands) which release secretions through ducts, endocrine glands are ductless and secrete hormones into blood circulation.
Functions of the Endocrine System
The endocrine system ensures:
• Growth and development
• Regulation of metabolism and energy levels
• Reproductive health
• Stress management
• Electrolyte and water balance
• Blood pressure control
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• Lood and sleep regulation
When hormones are balanced, the body functions smoothly. When imbalanced? It leads to endocrine disorders such as diabetes, hypothyroidism, infertility, obesity, and PCOS.
Major Endocrine Glands, Hormones & Functions
List of Primary Endocrine Glands
1. Hypothalamus
2. Pituitary gland
3. Pineal gland
4. Thyroid gland
5. Parathyroid glands
6. Adrenal glands
7. Pancreas (Endocrine part – Islets of Langerhans)
8. Gonads (Testes & Ovaries)
9. Thymus
1. Hypothalamus
Feature Details
Location Base of brain above pituitary
Hormones TRH, CRH, GnRH, GHRH, Dopamine, Somatostatin
Functions Links brain to endocrine system, regulates pituitary
Disorders Growth issues, behavioral problems, temperature dysregulation
Role: Master controller of hormonal feedback and homeostasis.
2. Pituitary Gland – “Master Gland”
Located below the hypothalamus, it controls other endocrine glands.
Anterior Pituitary Hormones
Hormone Function
GH Bone & muscle growth
TSH Stimulates thyroid hormone secretion
ACTH Regulates cortisol from adrenal glands
FSH & LH Reproduction – gamete formation & ovulation
Prolactin Milk production
Posterior Pituitary Hormones
Hormone Function
ADH Controls water balance & kidney function
Oxytocin Labor contraction & breastfeeding bonding
Disorders: Gigantism, acromegaly, infertility, diabetes insipidus
3. Pineal Gland
| Hormone | Melatonin | | Function | Sleep cycle, circadian rhythm, antioxidant | | Disorder | Sleep disturbance, jet lag, depression |
Releases more melatonin at night → induces sleep.
4. Thyroid Gland
Feature Details
Hormones T3, T4, Calcitonin
Functions Metabolism control, heart rate regulation, bone calcium balance
Disorders Hypothyroidism, hyperthyroidism, goiter
Thyroid dysfunction is one of the most common endocrine disorders worldwide.
5. Parathyroid Glands
| Hormone | Parathyroid hormone (PTH) | | Function | Increases blood calcium by bone resorption | | Disorders | Hypocalcemia, hypercalcemia, muscle cramps, kidney stones |
6. Adrenal Glands
Located above kidneys; involved in stress response and metabolism.
Cortex Hormones
Hormone Function
Cortisol Stress response, metabolism regulator
Aldosterone Electrolyte (Na+/K+) balance, BP control
Androgens Sex characteristics
Medulla Hormones
Hormone Function
Adrenaline (Epinephrine) Fight-or-flight response
Noradrenaline BP and heart regulation
Disorders: Cushing syndrome, Addison’s disease, adrenal tumors
7. Pancreas (Islets of Langerhans)
Cell Hormone Function
Beta cells Insulin Lowers blood sugar
Alpha cells Glucagon Raises blood sugar
Delta cells Somatostatin Inhibits GI hormones
Major disorder: Diabetes Mellitus
8. Gonads (Testes & Ovaries)
Gland Hormones Functions
Testes Testosterone Male sexual characteristics, sperm production
Ovaries Estrogen & Progesterone Menstrual cycle, pregnancy, female traits
Common disorders: PCOS, Infertility, Hypogonadism
9. Thymus
| Hormone | Thymosin | | Function | Development of T-cells (immune system) | | Note | Shrinks after puberty |
Summary Table: Endocrine Glands, Hormones & Functions
Endocrine Gland Major Hormones Key Functions Releasing Site
Hypothalamus TRH, CRH, GnRH, GHRH Controls pituitary Brain
Pituitary GH, TSH, ACTH, FSH, LH, Prolactin, ADH, Oxytocin Regulates other glands Brain
Pineal Melatonin Sleep regulation Brain
Thyroid T3, T4, Calcitonin Metabolism, calcium regulation Neck
Parathyroid PTH Calcium & phosphate balance Behind thyroid
Adrenal Cortisol, Aldosterone, Adrenaline Stress & BP control Above kidneys
Pancreas Insulin, Glucagon Blood sugar regulation Abdomen
Ovaries/Testes Estrogen, Progesterone, Testosterone Sexual functions Pelvic region
Thymus Thymosin Immune cell development Chest
How Endocrine System Is Regulated?
The body uses a feedback mechanism, especially negative feedback, to maintain hormone balance.
Example: Thyroid Hormone Regulation
Low T3/T4 → TRH (Hypothalamus) ↑ → TSH (Pituitary) ↑ → Thyroid hormones ↑ → Feedback stops TRH & TSH
Common Endocrine Disorders
Condition Affected Gland
Diabetes Mellitus Pancreas
Hypothyroidism / Hyperthyroidism Thyroid
PCOS Ovaries
Cushing Syndrome Adrenal cortex
Gigantism/Acromegaly Pituitary
Hypocalcemia/Hypercalcemia Parathyroid
Tips for Endocrine Health
• Maintain a balanced diet (iodine, vitamin D, calcium, zinc)
• Sleep 7–8 hours daily
• Regular exercise
• Stress management
• Avoid smoking & alcohol
Early medical checkups can detect hormone disorders before complications develop.
FAQs
1. What is an endocrine gland?
A ductless gland that releases hormones directly into the blood for body regulation.
2. How does the endocrine system differ from the nervous system?
Endocrine = Slow, long-lasting chemical signals
Nervous = Quick, short electrical signals
3. Which gland is known as the “master gland”?
Pituitary gland because it controls other endocrine glands.
4. Which endocrine gland controls metabolism?
Thyroid gland (T3 & T4 hormones)
5. Which hormones regulate blood sugar?
Insulin (lowers) and Glucagon (raises) — from pancreas.
6. What are the symptoms of hormonal imbalance?
Fatigue, weight changes, mood swings, irregular periods, sleep issues.
7. What gland shrinks after puberty?
Thymus gland
Conclusion
The endocrine system is the body’s powerful chemical control network. Each gland releases specific hormones that maintain health, growth, reproduction, and energy levels. Any disturbance in hormonal balance can lead to serious disorders, but early diagnosis, healthy lifestyle, and medical treatment help maintain normal hormonal functions.
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Writer: Vandita Singh, Lucknow (GS India Nursing Group)