Glands & Hormones: Biology PSC Notes

Glands & Hormones
A gland can be termed as an organ that produces and releases chemical substances into the bloodstream to perform a specific function in the body. The glands present in the human body can be hugely classified into two. They are
  • Endocrine glands – secretes hormones into the bloodstream.
  • Exocrine glands – release their secretions such enzymes, mucus, sebum, sweat, etc. into a duct.

Important Glands in the human body

The important endocrine glands and their secreted hormones that are essential for the proper functioning of the human body are as follows:

Adrenal gland

Adrenal gland
  • Also known as the 3F gland & 4S gland.
  • Cap-like triangular gland located above the kidney.
  • The adrenal gland is made up of 2 parts
    • Outer Adrenal cortex – makes hormones called corticosteroids that help control salt-water balance in the body, the immune system, metabolism, stress response, and sexual development and function.
      • There are 3 types of corticosteroids:
        • Glucocorticoids – Cortisol, Cortisone,
        • Mineral corticoids – Aldosterone (regulates sodium loss in the body),
        • Sex hormones
    • Inner Adrenal medulla – makes epinephrine/adrenaline & Noradrenaline which increases blood pressure and heart rate when the body is under stress.
  • Diseases
    • Addison's disease – deficiency of cortisol
    • Cushing's syndrome – overproduction of cortisol
    • Cons syndrome – the overdose of aldosterone
    • Vitiligo & Gynecomastia – due to the formation of tumors in the Adrenal gland.


  • Located at the lower central part of the brain.
  • Links the endocrine system and nervous system.
  • Made up of 3 parts
    • Anterior region also known as the supraoptic region regulates body heat and maintains the circadian rhythm. It consists of
      • Supraoptic nuclei.
      • Paraventricular nuclei.
    • Middle region also known as the tuberal region. It consists of
      • Ventromedial nuclei – controls the appetite.
      • Arcuate nuclei – released the growth hormone responsible for the growth and functioning of the human body.
    • Posterior region also known as the mammillary region. It consists of
      • Hypothalamic nucleus – cause shivering, blockage of sweat, and regulates the body temperature.
      • Mammillary nuclei – related to the memory function.

Pituitary gland

Pituitary gland
  • Also known as "master gland" & "hypophysis."
  • A pea-shaped gland at the base of the brain, just below the hypothalamus, close to the optic nerve.
  • Control & regulates other glands in the body.
  • It is divided into three lobes:
    • Anterior pituitary synthesis and secretion of hormones like ACTH, FSH / LH, HGH, TSH, Prolactin, MSH
    • Intermediate pituitary absent in adults.
    • Posterior pituitary synthesis and secretion of hormones like ADH & Oxytocin
  • Diseases
    • Acromegaly
    • Empty Sella Syndrome
    • Hypopituitarism

Thyroid‌ gland

Thyroid‌ gland
  • Ductless endocrine gland.
  • Butterfly shaped or bow-shaped gland located between C5 and T1 vertebrae in the neck.
  • Play a vital role in the development of the brain and nervous system as well as bone development in children.
  • Diseases
    • Goiter
    • Hyperthyroidism – Overproduction of thyroxine hormone.
    • Hypothyroidism – Underproduction of thyroxine hormone.
    • Thyroid cancer
      • Anaplastic thyroid cancer
      • Follicular thyroid cancer
      • Medullary cancer
      • Papillary thyroid cancer

Parathyroid gland

Parathyroid gland
  • Four tiny glands (3-5 mm in diameter & 30-60 mg in weight) attached to the thyroid gland.
  • Controls and regulates the calcium levels in the blood in the range between 9.0 & 10.1.
  • Releases 2 types of hormones – Parathormone & Calcitonin.
  • Diseases
    • Hyperparathyroidism – high levels of parathyroid hormone in the bloodstream.
    • Hypoparathyroidism – lower levels of parathyroid hormone in the bloodstream.


  • Gland located below the stomach and surrounded by the spleen.
  • Secretes digestive enzymes such as amylase, lipase & proteases.
  • Releases three hormones – Insulin, Glucagon & Somatostatin
  • Diseases
    • Pancreatitis
    • Pancreatic Cancer

Pineal gland

Pineal gland
  • A small pinecone-shaped gland located in the middle of the brain.
  • Also known as “the third eye.”
  • Regulates the body’s Circadian rhythm.
  • Produces white blood cells called T-lymphocytes that fight infection and hormone, Melatonin.
  • Diseases
    • Pineal Gland Tumors
    • Pineal Cysts

Reproductive Glands

Reproductive Glands
  • Male gonads aka testes –
    • Located in Scrotum.
    • Secretes male hormones called Androgens (Testosterone, Androstenedione & Inhibin).
  • Female gonads aka ovaries –
    • Located in Pelvis.
    • Secretes female hormones called Estrogen & Progesterone.

Thymus gland

Thymus gland
  • Pinkish-grey gland located deep within the chest.
  • Size varies according to age, larger in children, and smaller in adults.
  • Secretes hormones called Thymosin.
  • Diseases
    • Myasthenia gravis – abnormal enlargement of the thymus.
    • Pure red cell aplasia – occurs when there is a tumor in the thymus and the body attack its own stem cells.
    • Hypogammaglobulinemia – occurs when the body is producing not enough antibodies.
All these networks of glands and their secreted hormones together constitute the Endocrine System.

Glands & their hormones: In short

Adrenal glandAdrenaline, Noradrenaline, Aldosterone & Cortisol
HypothalamusVasopressin (aka Antidiuretic hormone),
GnRH (Gonadotropin-releasing hormone)
Pancreas‌Insulin, Glucagon & Somatostatin
Parathyroid glandParathyroid hormone
Pineal glandMelatonin, Serotonin (precursor to Melatonin)
Pituitary gland
  • ADH (Anti-Diuretic Hormone)
  • ACTH (Adrenocorticotrophic Hormone, Corticotropin)
  • FSH / LH (Follicle-Stimulating Hormone / Luteinising Hormone)
  • HGH (Human Growth hormone)
  • MSH (Melanocyte-Stimulating Hormone)
  • Oxytocin
  • Prolactin
  • TSH (Thyroid-stimulating hormone)
  • Thyrotropin
OvariesEstrogen & Progesterone
TestesTestosterone, Androstenedione & Inhibin
Thymus glandThymosin
Thyroid glandThyroxine (T4), Tri-iodothyronine (T3) & Calcitonin


  • Insulin shock – Lowering blood sugar level as far as 43mg / 100ml which leads to unconsciousness and sudden death.
    • also known as Severe hypoglycemia.
  • Vitiligo – a condition in which the skin loses its melanocytes, the pigment cells
  • Gynecomastia – Manifestation of femininity in males.