Endocrine System Study Guide

Adrenal Gland, Thyroid, Pancreas, and Pituitary Gland Overview

• The presentation begins by listing key glands: Adrenal gland, Thyroid, Pancreas, Pituitary gland, Brain, Ovary, Testicle, Thymus.

• The focus of the discussion is on glucose and hormonal regulation.

Exemplars of Related Conditions

• Key conditions to be discussed:

  • Diabetes Type 1 & Type 2

  • Hypo/hyperglycemia

  • Metabolic Syndrome

  • Starvation

  • Hypo/hyperthyroidism

  • Cushing’s Syndrome

  • Addison’s Disease

  • Syndrome of Inappropriate Antidiuretic Hormone (SIADH)

  • Diabetes Insipidus (DI)

Learning Objectives

• Laboratory Tests:

  • Identify tests for diagnosing Type 1 & Type 2 diabetes and metabolic syndrome.

• Complications Recognition:

  • Recognize complications from uncontrolled diabetes and untreated metabolic syndrome.

• Pathological Mechanisms:

  • Describe the mechanisms causing Type 1 and Type 2 diabetes.

• Signs & Symptoms:

  • Recognize clinical manifestations of both types of diabetes.

• Risk Factors:

  • Identify risk factors associated with Type 1, Type 2 diabetes, and metabolic syndrome.

• Disease Differentiation:

  • Differentiate diseases associated with pituitary, thyroid, and adrenal gland hyperfunction versus hypofunction.

• Hormones Origin:

  • Recognize hormones produced in anterior and posterior pituitary glands.

• Hypothalamus-Pituitary Hormone Axis:

  • Explain the hypothalamus-pituitary-hormone axis and its feedback mechanisms.

Hormone Cell to Cell Communication

• Paracrine Pathway:

  • Hormones act on nearby receptive cells after secretion.

• Autocrine Pathway:

  • Same as paracrine, with receptors on secretory cells allowing self-regulation.

• Endocrine Pathway:

  • Hormones travel through blood vessels to distant cells.

• Synaptic Pathway:

  • Neurotransmitters travel through axons to synapses affecting nearby neurons.

• Neuroendocrine Pathway:

  • Neurons release hormones into the vascular system to affect distant cells.

Hormone Cell to Cell Communication:

• Paracrine pathway:hormones are produced in a cell, secreted, and act directly on nearby receptive cells.

Autocrine pathway: the same as the paracrine pathway except that the receptor cells are also secretory cells so, in essence, the cell is able to produce the hormone and exert an effect on itself.

Endocrine pathway: hormones are produced in a cell, secreted, and travel through blood vessels to distant cells, attach to receptors, and act on that cell. Synaptic pathway: hormones (neurotransmitters) are produced in the neuron, secreted, and travel along the axon to the synapse where they are released and taken up by a nearby neuron with the appropriate receptors to exert an effect.

Neuroendocrine pathway: hormones (neurohormones) are produced in a neuron, secreted, travel along the axon to the synapse, are released, are taken up into the vascular system, and travel to distant cells with the appropriate receptors to exert an effect.

Interaction of Hypothalamus & Pituitary

• The hypothalamus produces various releasing and inhibiting hormones, stimulating the anterior pituitary and releasing pituitary hormones.

• Hormones produced in the hypothalamus include:

  • Corticotrophin-releasing hormone

  • Dopamine

  • Growth hormone-releasing hormone

  • Somatostatin

  • Gonadotrophin-releasing hormone

  • Thyrotrophin-releasing hormone

• Releasing hormones is a feedback reaction

• Posterior pituitary hormones (Oxytocin and ADH) are synthesized in the hypothalamus and stored before secretion into the bloodstream.

The hypothalamus produces several releasing & inhibiting hormones that act on the pituitary gland, stimulating the release of pituitary hormones.

The hormones produced in the hypothalamus are corticotrophin-releasing hormone, dopamine, growth hormone-releasing hormone, somatostatin, gonadotrophin-releasing hormone & thyrotrophin-releasing hormone.

Two hormones are produced by the hypothalamus & then stored in the posterior pituitary gland before being secreted into the bloodstream.

Hormones known as posterior pituitary hormones are synthesized by the hypothalamus, and include oxytocin and antidiuretic hormone (ADH or Vasopressin) The hormones are then stored in neurosecretory vesicles (Herring bodies) before being secreted by the posterior pituitary into the bloodstream.

Of the pituitary hormones, several act on other glands located in various regions of the body, whereas other pituitary hormones directly affect their target organs.

Regulatory Influences on Pituitary Gland

• Blood levels exert influences on the anterior pituitary.

• Releasing hormones:

  • Thyrotropin-releasing hormone (TRH)

  • Corticotropin-releasing hormone (CRH)

  • Gonadotropin-releasing hormone (GnRH)

  • Growth hormone-releasing hormone (GHRH)

Disorders of Pituitary Function

• Hypopituitarism & Growth Hormone Deficiency:

  • Inhibits somatic growth; dysfunction in the hypothalamus affects growth.

  • Signs include short stature, obesity, immature facial features, delayed puberty, hypoglycemia, seizures.

• Evaluation and Prognosis for GH Deficiency:

  • Diagnosis based on growth patterns, health history, and plasma GH levels via radioimmunoassay.

  • Prognosis for GH replacement shows 80% success with increased growth rates post-treatment.

• Pituitary Hyperfunction Clinical Manifestations:

  • Excess GH before epiphyseal closure results in overgrowth of long bones (gigantism), while after closure results in acromegaly.

Diabetes Insipidus (DI)

• Disorder due to hyposecretion of ADH causing uncontrolled diuresis with primary and secondary causes.

• Cardinal signs: Polyuria, polydipsia, dehydration.

• Treatment includes daily hormone replacement with Vasopressin (DDAVP).

Syndrome of Inappropriate Antidiuretic Hormone (SIADH)

• Pathophysiology includes hypersecretion of ADH, leading to fluid retention and hypotonicity.

• Symptoms include increased urine concentration and dilutional hyponatremia. Treatment includes fluid restriction and ADH antagonizing medications.

Diabetes Mellitus Type 1

• Characterized by an absolute deficiency of insulin due to autoimmune destruction of beta cells.

• Diagnostic tests include fasting blood glucose, glucose tolerance tests, and glycosylated hemoglobin (A1c).

• Clinical manifestations include polyuria, polydipsia, weight loss, hyperglycemia, and glucosuria.

• Ketoacidosis and treatment protocols for management.

Hypothyroidism and Hyperthyroidism

• Hypothyroidism:

  • Deficient thyroid hormones with clinical manifestations including fatigue, cold intolerance, and myxedematous skin changes.

  • Treatment with Levothyroxine.

• Hyperthyroidism (Graves' Disease):

  • Characterized by an enlarged thyroid and excessive metabolic activity.

  • Clinical manifestations include weight loss, sweating, and exophthalmos.

Cushing Syndrome and Adrenal Disorders

• Cushing's syndrome leads to excessive cortisol, possibly due to prolonged corticosteroid therapy or adenomas.

• Acute adrenocortical insufficiency can be life-threatening, requiring immediate treatment.

• Chronically, Addison's disease presents when 90% of adrenal tissue is nonfunctional requiring steroid replacement.

Metabolic Syndrome

• Associated with insulin resistance and includes obesity, dyslipidemia, and hypertension.

• Important to evaluate diabetes patients for this syndrome for comprehensive metabolic assessment.

Patient Education and Nursing Considerations

• Education should include understanding the disease, insulin therapy, dietary requirements, and managing acute complications.

• Recognize and support emotional and physical well-being during treatment adjustments and management of symptoms.

Endocrine Study Guide Chart Overview

• Hormones & Glands:

  • GH (Acromegaly), ADH (DI, SIADH), T3 & T4 (Myxedema Coma, Graves), PTH (Parathyroid disorders), Cortisol (Cushing’s & Addison’s), Insulin (Diabetes Mellitus).