MLT 234: Hormones

Overview of Class Interactions and Hormone Regulation

Introduction

  • Discussion about a student's performance in class.

    • The student has a price average of 600%.

    • The student claims that she will not fail due to upcoming clinical rotations.

    • Emphasis on the fact that passing is mandatory regardless of circumstances:

    • Rule: Must be above 75% to pass.

    • Attendance was notably limited (only five classes attended).

Importance of Class Attendance

  • Being in class is crucial for understanding course material.

  • The teacher encourages self-reflection on absences in a sixteen-week course.

Hormone Regulation: Protein vs. Steroid Hormones

  • Two types of hormone regulation:

    1. Protein Hormones

    • Receptor location: On the outer surface of the cell.

    • Mechanism: Utilizes a second messenger to transduce signals into the cell.

    1. Steroid Hormones

    • Receptor location: Located within the cell’s interior.

    • Mechanism: They can pass through the cell membrane unaided due to their lipophilic nature.

Feedback Mechanisms in Hormone Regulation

  • Discussed two types of feedback loops:

    1. Negative Feedback Loop

    • Definition: The end product reduces the initial action.

    • Function: Helps maintain homeostasis.

    • Example: End product in the endocrine hormone system inhibits further production from the hypothalamus and pituitary.

    1. Positive Feedback Loop

    • Definition: Reinforces processes until a specific end point is reached.

    • Function: Continues to promote the production of hormones until levels are sufficient, e.g., during labor.

Tropic vs. Direct Hormones

  • Tropic Hormones: Act on other endocrine glands to regulate hormone production.

  • Direct Hormones: Act directly on target tissues without intermediary glands.

Hormonal Outputs by Zone

  • Discussed adrenal gland zones and their respective final hormones:

    • G Zone: Produces aldosterone (regulates water and salt balance).

    • F Zone: Produces cortisol (involved in stress responses).

    • R Zone: Produces DHEA and DHEAS (precursor hormones for androgens like testosterone and estrogen).

Hormonal Testing and Conditions

  • Dexamethasone Suppression Test

    • High cortisol levels are examined:

    • Purpose: Determine if cortisol production can be suppressed.

    • Cortisol Stimulation Test

    • Conducted when cortisol levels are low:

      • Purpose: Stimulate adrenal glands to produce more cortisol using synthetic ACTH.

      • Test assesses pituitary function regarding ACTH production.

    • If failure occurs, further investigation of adrenal functionality is needed.

  • Use of these tests:

    • Dexamethasone suppression used primarily for diagnosing Cushing's syndrome.

  • Addison’s Disease: Associated with DHEAS levels.

  • Congenital Adrenal Hyperplasia: Results in excess DHEA production.

Menstrual Cycle Hormonal Changes

  • Hormonal fluctuation and functions during the menstrual cycle:

    • Follicle Stimulating Hormone (FSH):

    • Peaking around day 14, prior to ovulation.

    • Luteinizing Hormone (LH):

    • Surge coincides with ovulation peak.

    • If no pregnancy occurs, levels drop post-ovulation.

    • Estrogen and Progesterone:

    • Levels rise before ovulation; progesterone peaks approximately on day 22 during the luteal phase.

    • In pregnant females, estrogen and progesterone remain elevated throughout the pregnancy.

  • Amenorrhea: Absence of menstruation (no cycles).

  • Oligomenorrhea: Infrequent or irregular menstruation (cycles longer than 35 days).

Hypogonadism Types

  • Hypergonadotropic Hypogonadism: High gonadotropin levels but low sex hormones (often due to primary organ failure).

  • Hypogonadotropic Hypogonadism: Low gonadotropin levels leading to low sex hormone production (generally secondary to pituitary failure).

Thyroid Function and Disorders

  • Thyroid Gland Functions

    • Tissue growth, brain maturation, heat production, and increased metabolism.

  • Iodine Deficiency:

    • Leads to hypothyroidism named cognitive delay (formerly known as cretinism).

    • Emphasis on politically correct terminology.

  • Hypothalamic-Pituitary-Thyroid Axis:

    • Feedback loop: Adequate T4 and T3 suppress production of TSH and TRH.

Conditions Affecting Thyroid Function

  • Primary Hypothyroidism: Low T4 with high TSH.

  • Primary Hyperthyroidism: High T4 with low TSH.

  • Euthyroid Sick Syndrome: Normal thyroid lab results while displaying symptoms of thyroid dysfunction due to non-thyroid conditions.

    • Example: A patient with normal TSH but displaying signs of hypothyroidism due to autoimmune factors.

Thyroid Autoimmune Conditions

  • Hashimoto’s Disease: Autoimmune hypothyroidism where the body produces antibodies that attack the thyroid.

  • Graves’ Disease: Autoimmune hyperthyroidism characterized by antibody production that unregulated T4 release.

Organizing Hormonal Interactions

  • Primary Disorders: Issues with the target organ (e.g., thyroid).

  • Secondary Disorders: Issues arising from the pituitary affecting the organ (such as TSH dysfunction).

  • Tertiary Disorders: Issues arising from the hypothalamus affecting pituitary function.

Conclusion: Key Hormonal Interactions

  • Understanding how various hormones interact—the hypothalamus, anterior pituitary, and target organs—to regulate bodily functions effectively.