Article by Dr Manasa S, B.A.M.S
AIAPGET Points
- Hormones are chemical messengers produced by endocrine cells to regulate target tissues.
- Hormonal action depends on receptor presence and sensitivity, not hormone quantity alone.
- Hormones act through endocrine, paracrine, autocrine, juxtacrine, and intracrine mechanisms.
- Intracrine hormone action occurs within the cell without entering systemic circulation.
- Hormones are signaling molecules and do not provide energy or structural material.
- Hormones are effective in very small concentrations due to signal amplification.
- Hormones are classified as peptide, steroid, or amine based on chemical structure.
- Peptide hormones are water-soluble and act via membrane receptors.
- Steroid hormones are lipid-soluble and act through intracellular receptors.
- Water-soluble hormones act via second messenger systems such as cAMP, IP₃, DAG, and Ca²⁺.
- Lipid-soluble hormones directly influence gene transcription.
- Hormone secretion is commonly pulsatile rather than continuous.
- Loss of hormonal pulsatility can cause disease despite normal hormone levels.
- Hormones exhibit circadian, ultradian, and infradian rhythms.
- Only the free (unbound) fraction of a hormone is biologically active.
- Alterations in hormone-binding proteins can cause endocrine symptoms.
- Hormone resistance occurs due to receptor or post-receptor signaling defects.
- Endocrine disorders may exist with normal or elevated hormone levels.
- Hormone secretion is primarily regulated by negative feedback mechanisms.
- Hormones interact closely with the nervous and immune systems.
- Modern endocrinology views hormones as part of an integrated regulatory network.
Hormones – introduction & discussion – A Bird’s Eye View
Hormones are chemical messengers that coordinate and regulate various physiological functions in the body. They are produced and released by several glands, organs and tissues, many of which together form the endocrine system.
Hormones travel through the bloodstream to reach specific target organs, tissues or cells, where they convey precise instructions about what action to take and when. Through this mechanism, hormones play an essential role in maintaining health, balance and survival.
To date, scientists have identified more than 50 hormones in the human body, each with specific roles but often acting in coordination with others.
Functions of Hormones & Ayurveda outlook
Hormones regulate a wide range of vital body processes. Along with the endocrine tissues that produce them, they help maintain internal balance and ensure proper adaptation to internal and external changes.
Senior (late) Prof S.N.Ojha sir had correlated the functions of hormones with those of Vata and had considered hormonal functions as ‘Vata Dharmiya’ – ‘Vata-like’ in functions and actions.
Major functions regulated by hormones include:
Metabolism of carbohydrates, fats and proteins – appears to be the functions of Agni, Pachaka Pitta and Samana Vayu.
Homeostasis, including regulation of:
– Blood glucose
– Blood pressure
– Fluid and electrolyte balance
– Body temperature
Homeostasis – describe the functions similar to those of Samana Vayu.
Growth and development – this function can be attributed to all the three doshas because each dosha participates in its own ways in the growth and development of the child / fetus and also the maintenance of the same post-birth. This basically happens due to the varied interplay of Mahabhutas which make up the doshas. Kapha is the main dosha which helps in maintenance and sustenance of the growth and development. Vata helps in differentiation of body parts, the spacing in cells and organs and transportation while Pitta contributes in metabolism.
Sexual maturation and function – all three doshas with predominant involvement of kapha and vata shall be considered.
Reproduction – involves all three doshas & their interplay.
Sleep–wake cycle (circadian rhythm) – depends mainly on the Prana Vata-Udana Vata-Sadhaka Pitta- Tarpaka Kapha axis and its balance. It also depends on the dhatu samya – balance of dhatus and the resultant ojas (its qualitative and quantitative balance) and balance of functions of sense organs and mind.
Mood and emotional regulation – the same factors mentioned above in the context of sleep-wake cycle are also involved in this function.
An important feature of hormonal action is that very small quantities can produce significant physiological effects. Therefore, even minor increases or decreases in hormone levels can lead to marked clinical symptoms and disease states.
How Do Hormones Function?
Hormones exert their effects by acting as chemical signals that influence hundreds of interconnected physiological processes. Most bodily functions involve a cascade of hormonal interactions, rather than the action of a single hormone.
This also points towards the sama-dosha concept explained in Ayurveda which indicates not only balance of individual doshas but also relative balance of all three doshas and the interplay involving all the doshas.
A hormone can act only on tissues that possess specific receptors for it. This interaction is often explained using the “lock and key” model:
– The hormone acts as the key
– The receptor on the target cell acts as the lock
Only when the hormone fits its receptor can it deliver its message, triggering a specific cellular response.
This probably reflects the knowledge of ashraya-ashrayi bhava i.e. the residence-resident relationship between the dushya (tissues – ashraya) and dosha (hormones? – ashrayi). Diseases are also caused when the tissues are disturbed by aggravated doshas according to Ayurveda.
Types of Hormonal Communication
The body uses hormones for two main types of communication:
-
Inter-Endocrine (Gland-to-Gland) Communication
In this type, one endocrine gland releases a hormone that regulates the activity of another endocrine gland.
Example:
The pituitary–thyroid axis
– The pituitary gland secretes thyroid-stimulating hormone (TSH)
– TSH stimulates the thyroid gland to release thyroid hormones (T₃ and T₄)
– These hormones then regulate metabolism and energy balance throughout the body
This type of communication forms the basis of endocrine axes and feedback mechanisms, which are crucial for exam understanding.
From the Ayurveda perspective, it can be considered as the Prana-Udana Vayu axis.
-
Endocrine Gland–to–Target Organ Communication
Here, a hormone acts directly on non-endocrine target tissues to produce a physiological effect.
Example:
– The pancreas releases insulin
– Insulin acts on muscle, liver and adipose tissue
– It facilitates glucose uptake and utilization, thereby regulating blood sugar levels
Types of Hormones
Hormones are classified based on their chemical structure and solubility:
-
Steroid Hormones
Steroid hormones are synthesized from cholesterol and are not water-soluble. They readily cross cell membranes and act via intracellular receptors.
Examples:
– Estrogen
– Testosterone
-
Peptide Hormones
Peptide hormones consist of three or more amino acids and are water-soluble. They act through membrane-bound receptors.
Examples:
– Antidiuretic hormone (ADH) – involved in water balance and metabolism
– Oxytocin – plays a key role in childbirth and lactation
– Insulin and insulin-like growth factors – regulate blood glucose levels
-
Amine Hormones
Amine hormones are derived from amino acids. Some are water-soluble, while others are lipid-soluble.
Examples:
– Thyroid hormones
– Epinephrine
– Norepinephrine
– Dopamine
Tissues that produce Hormones
Endocrine Glands (Classical Endocrine System)
Endocrine glands release hormones directly into the bloodstream and include:
– Hypothalamus
– Pituitary gland
– Pineal gland
– Thyroid gland
– Parathyroid glands
– Adrenal glands
– Pancreas
– Ovaries
– Testes
Hypothalamus
The hypothalamus is a small but crucial region of the brain that links the nervous system and endocrine system. It controls the pituitary gland via releasing and inhibitory hormones.
Hormones produced by the hypothalamus include:
– Corticotropin-releasing hormone (CRH)
– Dopamine
– Gonadotropin-releasing hormone (GnRH)
– Growth hormone-releasing hormone (GHRH)
– Somatostatin
– Thyrotropin-releasing hormone (TRH)
– Oxytocin (synthesized here, released by posterior pituitary)
Pituitary Gland (Master Gland)
The pituitary gland is a pea-sized gland located at the base of the brain. It has two lobes:
Anterior Pituitary Hormones:
– Adrenocorticotropic hormone (ACTH)
– Follicle-stimulating hormone (FSH)
– Growth hormone (GH)
– Luteinizing hormone (LH)
– Prolactin
– Thyroid-stimulating hormone (TSH)
Posterior Pituitary Hormones:
– Antidiuretic hormone (ADH / vasopressin)
– Oxytocin
Pineal Gland
– Secretes melatonin
– Regulates sleep–wake (circadian) rhythm
Thyroid Gland
Located in the front of the neck, the thyroid gland regulates basal metabolic rate.
Hormones released:
– Thyroxine (T4)
– Triiodothyronine (T3)
– Reverse T3 (rT3)
– Calcitonin
Parathyroid Glands
– Usually four glands located behind the thyroid
– Secrete parathyroid hormone (PTH)
– Regulate calcium and phosphate metabolism
Adrenal Glands
Situated above the kidneys, adrenal glands produce:
– Cortisol
– Aldosterone
– Adrenal androgens (DHEA)
– Adrenaline (epinephrine)
– Noradrenaline (norepinephrine)
Pancreas (Endocrine Function)
The islets of Langerhans secrete:
– Insulin
– Glucagon
These hormones play a vital role in blood glucose regulation.
Sex Hormones
Female Sex Hormones
Female sex hormones are more abundant in females than males, although they are present in both sexes to some extent. These hormones play a crucial role in sexual differentiation, puberty, menstrual cycle regulation, fertility, pregnancy, and secondary sexual characteristics.
Major Female Sex Hormones
The principal female sex hormones include:
- Estrogens
Secreted mainly by ovaries (also by adipose tissue and placenta)
Functions:
– Development of female secondary sexual characteristics
– Proliferation of endometrium
– Regulation of menstrual cycle
– Maintenance of bone health
– Influence on libido
- Progesterone
Secreted by corpus luteum and placenta
Functions:
– Prepares endometrium for implantation
– Maintains pregnancy
– Thickens cervical mucus
– Inhibits uterine contractions
- Follicle-Stimulating Hormone (FSH)
Secreted by anterior pituitary
Functions:
– Stimulates growth and maturation of ovarian follicles
– Promotes estrogen synthesis in ovaries
Exam point: FSH → follicular development
- Luteinizing Hormone (LH)
Secreted by anterior pituitary
Functions:
– Triggers ovulation
– Formation of corpus luteum
– Stimulates progesterone secretion
Exam point: LH surge → ovulation
Hormonal Regulation
– Female reproductive hormones are regulated through the Hypothalamo–Pituitary–Ovarian (HPO) axis
– GnRH → FSH & LH → Ovarian hormones (Estrogen, Progesterone)
– Feedback mechanisms (negative & mid-cycle positive feedback) regulate hormone secretion
Clinical & Physiological Notes
Hormone levels fluctuate cyclically during the menstrual cycle
Major hormonal shifts occur during:
– Puberty
– Pregnancy
– Menopause
Disorders like PCOS, amenorrhea, infertility involve imbalance of FSH, LH, estrogen, and progesterone
Important Points –
FSH promotes follicular growth, LH induces ovulation, estrogen proliferates endometrium, and progesterone maintains pregnancy.
Male Sex Hormones
Primarily produced by testes (under pituitary control):
– Testosterone
Luteinizing Hormone (LH)
Follicle-Stimulating Hormone (FSH)
Key functions:
– Testosterone
– Development of male secondary sexual characteristics
– Muscle and bone development
– Maintenance of libido
– Supports spermatogenesis
Luteinizing Hormone (LH) – Stimulates Leydig cells to secrete testosterone
Follicle-Stimulating Hormone (FSH)
– Acts on Sertoli cells
– Essential for spermatogenesis
Exam note:
FSH → Sertoli cells
LH → Leydig cells
Other Hormone Producing Tissues
Adipose Tissue
Produces:
– Leptin
– Adiponectin
– Estrogen
– Angiotensin
Kidneys
Produce:
– Erythropoietin
– Renin
– Active vitamin D (calcitriol)
Liver
Produces:
– Insulin-like growth factor-1 (IGF-1)
– Angiotensinogen
Gastrointestinal Tract
Produces:
– Ghrelin
– Somatostatin
– GLP-1
Placenta
Temporary endocrine organ producing:
– Estrogen
– Progesterone
Conditions Caused by Hormonal Imbalance
Hormonal imbalance can lead to a wide range of medical conditions. For most hormones, both deficiency and excess can produce characteristic clinical features and disease states. These imbalances often require medical evaluation and appropriate treatment.
Common hormone-related conditions include:
– Diabetes mellitus — Type 1 diabetes, Type 2 diabetes and gestational diabetes
– Thyroid disorders — Hypothyroidism (deficiency of thyroid hormones) and hyperthyroidism (excess thyroid hormones)
– Menstrual disorders — Polycystic ovary syndrome (PCOS), amenorrhea and anovulation
– Female infertility
– Male infertility, commonly due to low testosterone levels (hypogonadism)
– Obesity and metabolic disorders
Causes of Hormonal Imbalance
Hormonal imbalances can arise due to multiple underlying causes. Common etiological factors include:
– Tumors, adenomas or abnormal growths of endocrine glands
– Damage or injury to endocrine tissues
– Autoimmune disorders affecting hormone-producing glands
– Genetic or hereditary mutations that alter hormone synthesis, secretion or receptor function
Clinical Features Suggestive of Hormonal Imbalance
A hormonal imbalance may be suspected when an individual presents with one or more of the following features:
– Difficulty conceiving or maintaining pregnancy
– Irregular or absent menstrual cycles
– Unexplained changes in energy levels, sleep pattern or libido
– Significant mood fluctuations
– Persistent skin problems such as acne or dryness
– Heat or cold intolerance
– Symptoms involving multiple organ systems
– Unexplained weight gain or weight loss
Important note for exams and clinical practice
Symptoms alone are not sufficient to diagnose hormonal imbalance, as many endocrine disorders present with overlapping features. Biochemical evaluation and hormonal assays are essential for confirmation.
Healthcare Providers for Hormone-Related Conditions
Many hormone-related conditions can be initially evaluated and managed by primary healthcare providers. However, specialized care is often required.
– An endocrinologist is a medical specialist trained in diagnosing and treating disorders of the endocrine system.
– Endocrinologists manage conditions related to hormone excess, deficiency, and resistance, and design long-term treatment and monitoring plans.
For Further Readng
https://www.easyayurveda.com/2014/06/22/ashwagandha-withania-somnifera-benefits-dose-side-effects/
https://www.easyayurveda.com/2024/01/17/amla-amalaki-womens-health/
https://www.medicalnewstoday.com/articles/what-are-hormones#types
https://my.clevelandclinic.org/health/articles/22464-hormones
https://www.hopkinsmedicine.org/health/conditions-and-diseases/hormones-and-the-endocrine-system
https://www.nature.com/subjects/hormones
https://pmc.ncbi.nlm.nih.gov/articles/PMC10031253/
https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2024.1340432/full
Quick Revision points
– Hormones are chemical messengers produced by endocrine glands and certain tissues that regulate and coordinate physiological functions of the body.
– They act through the bloodstream, reaching specific target organs, tissues or cells that possess appropriate receptors.
– Hormonal action is highly specific, explained by the “lock and key” mechanism — only cells with matching receptors respond to a hormone.
– Very small quantities of hormones produce powerful effects, hence even minor imbalances can result in significant clinical disorders.
– Hormones function in integrated networks, often through endocrine axes involving the hypothalamus, pituitary and peripheral glands.
– Hormonal regulation is primarily controlled by feedback mechanisms, especially negative feedback, which maintains internal homeostasis.
– Hormones regulate essential life processes, including metabolism, growth, development, reproduction, stress response, sleep and mood.
– They are classified chemically into steroid, peptide and amine hormones, which differ in solubility, receptors and mechanism of action.
– Apart from classical endocrine glands, several tissues act as endocrine organs, including adipose tissue, kidneys, liver, gastrointestinal tract and placenta.
– Hormonal imbalance—either deficiency or excess—leads to disease, making hormones central to understanding endocrine, metabolic and reproductive disorders.
