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Chemical Coordination and Integration - Hypo-and hyperactivity and related disorders

Grade 11CBSEBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Hyposecretion refers to the underproduction of a hormone, while hypersecretion refers to the overproduction, both leading to physiological imbalances.

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Pituitary Gland Disorders: Hyposecretion of Growth Hormone (GHGH) during childhood leads to Pituitary Dwarfism. Hypersecretion in childhood leads to Gigantism, while hypersecretion in adults causes Acromegaly (disfigured face/limbs).

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Thyroid Gland (Hypothyroidism): Iodine deficiency causes Simple Goitre. Hypothyroidism during pregnancy leads to Cretinism (stunted growth, mental retardation). In adults, it may cause Myxedema (Puffiness, low BMRBMR).

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Thyroid Gland (Hyperthyroidism): Graves' disease (Exophthalmic Goitre) is characterized by protrusion of eyeballs, increased Basal Metabolic Rate (BMRBMR), and weight loss.

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Adrenal Gland Disorders: Hyposecretion of corticoids (Glucocorticoids and Mineralocorticoids) leads to Addison's disease, characterized by acute fatigue, bronze skin pigmentation, and low blood pressure.

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Pancreatic Disorders: Hyposecretion of Insulin or cellular insensitivity results in Diabetes Mellitus, leading to Hyperglycemia, Glycosuria (glucose in urine), and formation of ketone bodies.

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Parathyroid Gland Disorders: Hyposecretion of Parathyroid Hormone (PTHPTH) leads to Parathyroid Tetany (muscle spasms due to low blood Ca2+Ca^{2+} levels).

📐Formulae

Total T4=Thyroxine (Tetraiodothyronine)\text{Total } T_4 = \text{Thyroxine (Tetraiodothyronine)}

Total T3=Triiodothyronine\text{Total } T_3 = \text{Triiodothyronine}

BMR∝[T3]+[T4]\text{BMR} \propto [T_3] + [T_4]

↓Insulin  ⟹  ↑Blood Glucose>180 mg/dL (Renal Threshold)\downarrow \text{Insulin} \implies \uparrow \text{Blood Glucose} > 180 \text{ mg/dL (Renal Threshold)}

↓PTH  ⟹  ↓[Ca2+]plasma  ⟹  Tetany\downarrow PTH \implies \downarrow [Ca^{2+}]_{\text{plasma}} \implies \text{Tetany}

💡Examples

Problem 1:

A 35-year-old patient presents with protruding eyeballs, a rapid heart rate, and significant weight loss despite a normal diet. Identify the probable disorder and the hormone responsible.

Solution:

The disorder is Exophthalmic Goitre (Graves' Disease), caused by the hypersecretion of Thyroid hormones (T3T_3 and T4T_4).

Explanation:

Hyperthyroidism increases the Basal Metabolic Rate (BMRBMR), leading to rapid depletion of energy stores (weight loss) and increased cardiac activity. The protrusion of eyeballs (Exophthalmos) is a classic sign of this autoimmune hyperthyroid condition.

Problem 2:

Explain why a deficiency in Iodine in the diet leads to an enlarged thyroid gland (Goitre).

Solution:

Low Iodine →\rightarrow Low T3/T4T_3/T_4 →\rightarrow Lack of negative feedback →\rightarrow High TSHTSH →\rightarrow Hyperplasia of Thyroid.

Explanation:

Iodine is essential for the synthesis of T3T_3 and T4T_4. When levels are low, the Pituitary gland secretes more Thyroid Stimulating Hormone (TSHTSH) to compensate, which causes the thyroid gland to enlarge in an attempt to capture more iodine.

Hypo-and hyperactivity and related disorders Revision - Class 11 Biology CBSE