Hypothalamus & Pituitary Disease

OBJECTIVES

  • Briefly review anatomy of the hypothalamus

  • Briefly review anatomy of the pituitary

  • Review hormones released from each structure and their target organ

  • Discuss signs and symptoms that develop with dysfunction of the hypothalamus and pituitary gland

  • Review various diseases that result from dysfunction of these structures

  • Review conditions that affect the hypothalamus and pituitary

HYPOTHALAMUS

Anatomy

  • Located on top of the brainstem and at the center of the brain.

  • Part of the diencephalon.

  • Borders:

    • Rostral: optic chiasm, lamina terminalis, anterior commissure

    • Posterior: mammillary bodies

    • Inferior: tuber cinereum tapering into median eminence leading to infundibular stalk

    • Lateral: defined by the internal capsule

    • The 3rd ventricle is situated in the midline.

Function

  • Maintains homeostasis by controlling endocrine and autonomic functions.

  • Regulates:

    • Body temperature

    • Weight and appetite

    • Childbirth and lactation

    • Growth

    • Sleep-wake cycle

    • Sexual drive

    • Emotion regulation

Homeostatic Functions

  • Temperature Regulation:

    • Normal temperature approx. 37°C.

    • Body response to temperature changes:

    • Heat: sweating.

    • Cold: shivering.

Hypothalamic Regions

  1. Anterior:

    • Autonomic control

    • Neuroendocrine control

  2. Tuberal (Middle):

    • Feeding/satiety

  3. Posterior:

    • Sympathetic tone

    • Memory/learning

Anterior and Medial Nuclei Functions

  • Control parasympathetic responses:

    • Decrease in heart rate.

    • Increase in secretion of saliva.

    • Pupillary constriction.

Posterior and Lateral Hypothalamus Functions

  • Control sympathetic responses:

    • Increased heart rate.

    • Increased blood pressure.

    • Pupillary dilation.

Nuclei of the Hypothalamus

  • Anterior (5 nuclei):

    • Preoptic: Gonadotropin-releasing hormone (GnRH)

    • Paraventricular: Oxytocin, vasopressin, CRH, TRH

    • Supraoptic: Vasopressin, oxytocin

    • Suprachiasmatic: Circadian rhythms

    • Anterior hypothalamic: Body temperature

  • Middle/Tuberal (3 nuclei):

    • Arcuate: Growth hormone-releasing hormone (GHRH), prolactin-inhibiting hormone (dopamine)

    • Ventromedial: Satiety

    • Dorsomedial: Emotional response, blood pressure control

  • Posterior (2 nuclei):

    • Mammillary: Emotion, memory

    • Posterior hypothalamic: Blood pressure regulation, thermoregulation

Connection Between Hypothalamus and Pituitary

  • Magnocellular regions of the supraoptic and paraventricular nuclei produce oxytocin and vasopressin, transported via axonal systems to posterior pituitary.

  • Hormonal signals to anterior pituitary are transported via the tuberoinfundibular tract.

Evaluation of Dysfunction

  • Causes of dysfunction may include:

    • Brain surgery

    • Traumatic brain injury

    • Brain tumors

    • Radiation

    • Genetic disease

    • Nutritional deficiency

    • Infection and inflammation

PITUITARY GLAND

Anatomy

  • Pea-sized gland located in middle cranial fossa within the sella turcica of the sphenoid bone.

  • Consists of two lobes: anterior and posterior pituitary.

  • Superiorly bounded by the optic chiasm and laterally by the cavernous sinus.

Neurosecretory Cells Functions

  • Anterior pituitary hormones:

    • ACTH (Adrenocorticotropic hormone)

    • Prolactin

    • Growth Hormone (GH)

    • Thyroid Stimulating Hormone (TSH)

    • Follicle Stimulating Hormone (FSH)

    • Luteinizing Hormone (LH)

  • Posterior pituitary hormones:

    • Oxytocin

    • Vasopressin (ADH)

Hormonal Control Mechanism

  • Anterior pituitary hormones are released into the portal circulation, regulated by releasing and inhibiting hormones from the hypothalamus.

  • Hormones secreted from axon endings of the posterior pituitary enter the bloodstream directly.

Pituitary Diseases
Mass Lesions

  • Include adenomas, cysts, or metastatic cancers affecting pituitary function.

Tumors Classification

  • Tumors categorized by cell origin and size:

    • Microadenomas: <1 cm

    • Macroadenomas: ≥1 cm

Neurologic Symptoms of Pituitary Tumors

  • Visual impairment due to optic chiasm compression leading to visual field loss (bitemporal hemianopsia).

  • Headaches due to tumor pressure.

Pituitary Apoplexy

  • A medical emergency due to sudden hemorrhage in a pituitary macroadenoma presenting with severe headache, neck stiffness, and visual changes.

Presentations of Pituitary Tumors

  • Can lead to:

    • Central diabetes insipidus

    • Hormonal deficiencies (e.g., growth hormone, gonadotropins)

    • Hormonal excess (e.g., Cushing's Disease, gigantomachy, galactorrhea)

  • Acromegaly caused by excessive secretion of growth hormone.

Evaluation of Pituitary Function

  • Serum hormone analysis and imaging (MRI) for structural abnormalities.

Conclusion

  • Proper evaluation and management of hypothalamic and pituitary dysfunction are crucial for maintaining endocrine health and addressing syndromes effectively.

Key Disorders

  • SIADH (Syndrome of Inappropriate Antidiuretic Hormone)

  • Cerebral Salt Wasting

  • Diabetes Insipidus

  • Wolfram Syndrome

  • Prader-Willi Syndrome

  • Kallman Syndrome

Treatments

  • Hormonal replacements and surgical interventions where applicable, alongside supportive care for symptom management.

Contact Information

  • Christina Lenk, MD

  • Email: 65201@yahoo.com