Importance of hormones in development and growth of the human and animals.pdf

This presentation is for medical students and medical professionals

1. FROM EMBRYO TO ADULTHOOD IN HUMANS AND ANIMALS
FARAZ WASIM (Neurosurgeon )
department of Clinical Anatomy
Tashkent Medical university
Termiz branch
Ex: lecturer in Pakistan National
Medical University ISB
department of Traumatology and
Neurosurgery
Chemical Conductors: The Pivotal Role of
Hormones in Growth and Development

2. The Blueprint and The Conductor s
The Blueprint and The Conductor
· We have a genetic blueprint (DNA), but how is this
blueprint executed in a precise temporal and spatial
manner?
· How do different parts of the body "know" when to
grow, change, and mature?
· Answer: The Endocrine System.
· Hormones are the chemical messengers that
conduct this complex symphony of life.

3. The Endocrine System: A Primer
The Signaling Network
Definition: A system of glands (endocrine glands)
that secrete hormones directly into the
bloodstream.
Key Properties of Hormones:
Specificity: Act on specific target cells with
compatible receptors.
Potency: Effective in very low concentrations.
Integration: Work in complex, interconnected
feedback loops.
Major Glands: Hypothalamus, Pituitary, Thyroid,
Adrenals, Pancreas, Gonads (Testes/Ovaries).

4. The Master Gland: The Pituitary and
its Trophic Hormones
Controlled by the hypothalamus.
Secretes "trophic" hormones that stimulate other glands.
Key Hormones for Growth/Development:
Growth Hormone (GH): Stimulates overall body growth.
Thyroid-Stimulating Hormone (TSH): Signals the thyroid
gland.
Prolactin (PRL): Essential for mammary gland development
and milk production.
Gonadotropins (FSH/LH): Control the gonads (puberty and
reproduction).

5. The Powerhouse of Metabolism:
Thyroid Hormones
Thyroid Hormones: The Engines of Metabolism and
Brain Development
Thyroid Hormones: The Engines of Metabolism and
Brain Development
Hormones: Thyroxine (T4) and Triiodothyronine
(T3).
Crucial Roles:
Fetal & Neonatal Development: Critical for the
development of the central nervous system.
Deficiency can lead to irreversible intellectual
disability (Cretinism).
Metabolic Rate: Regulates basal metabolic rate
(BMR), impacting energy utilization and heat
production.
Growth: Synergizes with Growth Hormone to
promote skeletal growth and maturation.

6. The Primary Driver The Primary Driver of Linear
Growth: Growth Hormone (GH Linear Growth:
Growth Hormone (GH
Growth Hormone: Building
the Body's Framework
The Primary Driver of
Linear Growth: Growth
Hormone (GH)
Direct Effects: Stimulates liver and other tissues to produce Insulin-like Growth Factor 1 (IGF-1).
IGF-1 is the primary mediator of GH's growth-promoting effects.
Actions of GH/IGF-1 Axis:
Stimulates protein synthesis (muscle growth).
Promotes proliferation of chondrocytes (cartilage cells) in growth plates, driving long bone
elongation.
Mobilizes fats for energy.

7. Study in Humans: Growth Disorders
· Title: Clinical Evidence: When Hormonal Signaling Fails
Growth Hormone Deficiency:
In children, results in Pituitary Dwarfism
(proportionate short stature).
Growth Hormone Excess:
In children: Gigantism (excessive
height).
In adults (after growth plates fuse):
Acromegaly (enlargement of hands, feet,
and facial features).
Treatment: Synthetic GH is successfully used to
treat deficiency.
Study in Humans: Growth Disorders
Clinical Evidence: When Hormonal Signaling Fails

8. The Transition to Adulthood:
Sex Hormones
Puberty: The Hormonal Awakening
Trigger: Re-activation of the
Hypothalamic-Pituitary-
Gonadal
(HPG) axis
Androgens (e.g
Testosterone):Deepening of voice,
muscle growth, facial/pubic hair,
sperm production
Estrogens (e.g., Estradiol): Breast
development (thelarche),
widening of hips, onset of
menstruation (menarche).
Both: Growth spurt, bone
maturation, and closure of growth
plates.

9. Hormonal Control of Life Cycles in Animals Beyond Humans: Hormones Shape Animal Life
Histories
Metamorphosis in Amphibians:
Thyroxine (T4) is the master regulator of frog
metamorphosis (tadpole to frog).
Prolactin can antagonize this process.
Insect Molting and Metamorphosis:
Ecdysone (Molting Hormone) triggers shedding of
the exoskeleton.
Juvenile Hormone (JH): High levels ensure larval
stages; decreasing levels permit metamorphosis to
the pupal and adult stages.

11. Hormonal Orchestration of Mammalian
Lactation Content:
Mammary Gland Development:
Estrogen and Progesterone during
pregnancy.
Milk Synthesis (Lactogenesis): Driven by
Prolactin.
Milk Ejection (Let-down): Mediated by
Oxytocin in response to suckling.
This is a perfect example of sequential
and synergistic hormonal control for a
key developmental process (nourishing
the young). A Unique Mammalian
Example: Lactation

12. Hormonal environment in the womb can
"program" long-term health.
Example: Glucocorticoids (e.g Cortisol)
Essential for maturing fetal organs
(especially lungs) late in gestation.
However, excessive maternal
stress/cortisol can cross the placenta and is
associated with a higher risk of the
offspring developing hypertension,
metabolic syndrome and anxiety disorders
in adulthood.The Fetal Environment: Prenatal Hormonal Programming
· Title: Developmental Origins of Health and Disease (DOHaD)

13. PTH (from Parathyroid glands): Raises blood
calcium levels by breaking down bone (osteoclast
activity) and promoting calcium reabsorption in
kidneys. Essential for mineral homeostasis.
Calcitonin (from Thyroid): Lowers blood
calcium by inhibiting osteoclasts.
More significant in young animals and during
pregnancy/lactation.
Vitamin D (a pro-hormone): Crucial for
calcium absorption from the gutThe Silent Support: Calcium and Bone Metabolism
Parathyroid Hormone (PTH) and Calcitonin: Guardians of
Skeletal Integrity

14. When Balance is Lost: Endocrine
Disrupting Chemicals (EDCs)
A Modern Threat: Synthetic Chemicals and
Hormonal Harmony
EDCs: Man-made chemicals that can mimic,
block, or interfere with the body's hormones.
Examples: Bisphenol A (BPA), Phthalates, DDT.
Impacts on Development:
Abnormal reproductive organ development.
Early puberty.
Reduced fertility.
Neurological and immune effects.
Evidence from wildlife (e.g intersex fish) and
human epidemiological studies.

15. Synthesis and Key Takeaways
Summary: The Unseen Symphony
Hormones are indispensable chemical
conductors from conception to
senescence.
They act in a precise, integrated cascade
(e.g.HPG, HPA axes)
They control critical windows of
development (e.g.thyroid in brain, sex
hormones in puberty).
Their effects are seen across the animal
kingdom, demonstrating deep evolutionary
roots.
Balance is everything: deficiency or excess
leads to profound disorders.
Understanding this system is crucial for
medicine, agriculture, and environmental
health.