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Pituitary & Adrenals

PITUITARY AND ADRENAL GLANDS

The pituitary gland (aka hypophysis) is a small “pea sized” gland that is connected the the base of the brain (hypothalamus) by the pituitary stalk.  The pituitary gland is enclosed in a bony cavity called the sella turcica. The pituitary gland is considered the “master gland” and divided into two parts : anterior and posterior pituitary.

 

ANTERIOR PITUITARY produces

  • Growth Hormone (GH, Human GH)

    • Stim­u­lates growth of the entire body but espe­cially effective at epi­phy­seal plates in youth needed for growth (height)

    • Strengthens and increases mineralization of bone

    • Increases muscle mass and protein synthesis (anabolic)

    • Promotes lipolysis

    • Clinical Conditions:

      • Growth Hormone Excess

        • Somatotropic Adenoma (GH producing tumor)

          • Arcomegaly

          • Gigantism

            • Treatment: Medication, Radiation, Surgery, Chemo

      • Growth Hormone Deficiency

        • Hypopituitarism (Surgical, Head trauma, Space occupying lesion, Infiltrate)

          • Growth Hormone Deficiency

          • Dwarfism

            • Treatment: Growth Hormone Replacement

  • Thyroid Stimulating Hormone (TSH; Thyrotropin)

    • Has two subunits

      • alpha (identical to hCG, LH, FSH)

      • beta

    • Sig­nals the thy­roid to pro­duce thy­roid hormone.

  • Clinical conditions:

  • Excess

    • Thyrotrophic Adenoma (TSH producing tumor)

      • Hyperthyroidism

        • Treatment: Radiation, Surgery

      • Deficiency

        • Hypopituitarism (Surgical, Head trauma, Space occupying lesion, Infiltrate)

        • Hypothyroidism

          • Treatment: Thyroid hormone replacement

  • Adrenocorticotropic Hormone (ACTH)

    • Stimulates ADRENAL GLAND to secrete Cortisol (glucocorticoid steroid hormone) which is a “stress hormone” from predominantly zona fasciculate of the adrenal cortex.

    • Clinical conditions

      • Excess

        • Corticotrophic Adenoma (CRH producing tumor)

          • Central Cushing’s Disease = Central Hypercortisolism

          • Treatment: Medication, Radiation, Surgery, Chemo      

      • Deficiency

        • Hypopituitarism (Surgical, Head trauma, Space occupying lesion, Infiltrate)

          • Central Adrenal Insufficiency or Secondary Adrenal Insufficiency. Addison’s disease = adrenal insufficiency

            • Treatment: Cortisol replacement therapy

  • Gonadotropins (LH & FSH)

    • Hormones released are Luteinizing hormone (LH) and Follicle Stimulating Hormone (FSH)

      • Luteinizing Hormone

        • Females: Triggers ovulation, and development of corpus luteum

        • Males: Stimulates Leydig cell production of Testosterone

      • Follicle Stimulating Hormone

        • Females: Initiates follicular growth and affects granulosa cells

        • Males: Induces Sertoli cells to secrete inhibin and stimulate formation of sertoli-sertoli tight junctions  

  • Prolactin (PRL)

    • Predominantly secreted from pituitary lactotrophic cells

    • Stimulated by TRH in addition to other neurochemicals

    • Inhibited by Dopamine

    • Stimulate mammary gland to produce milk (lactation)

      • Excess (hyperprolactinemia) from tumor, stalk involvement, medications or decreased clearance

        • Females: menstrual irregularity, infertility, lactation, visual problems (pituitary tumor), loss of libido

        • Males – Visual problems, erectile dysfunction, loss of libido 

  • Melanocyte-Stimulating Hormone (MSH)

    • Released from pars intermedia of the pituitary

    • Synthesized from same precursor molecule (POMC) as ACTH

    • Stimulates the production and release of melanin by melanocytes in skin and hair

    • Signals brain to have effects on appetite and sexual arousal

 

POSTERIOR PITUITARY stores and secretes following molecules

  • Arginine Vasopressin (AVP, Vasopressin, Anti-diuretic hormone, ADH)

    • Retain water in the body and to constrict blood vessels

      • Diabetes Insipidus is a deficiency resulting in following symptoms

        • Excessive thirst, excessive urination, dry mouth and fatigue

  • Oxytocin

    • Causes uterine contraction

The pituitary gland also works on a negative feedback mechanism that helps regulate production of precursor hormones.

 

ADRENAL GLANDS are located on top of both kidneys and are responsible for releasing hormones in response to stress.

  • Adrenal Cortex produces

    • Corticosteroids (cortisol) – “stress hormone”

      • Deficiency from autoimmune, infectious/infiltration, cancer,  medication, bleeding, genetic cause:

        • Primary Adrenal Insufficiency

        • Symptoms: Nausea, vomiting, weight loss, anorexia, abdominal pain, fatigue, fever, confusion/coma, electrolyte abnormality, generalized weakness, low blood sugar (hypoglycemia)

      • Excess production is due to adenoma, carcinoma or hyperplasia and cause

        • Adrenal Cushing’s (aka ACTH independent Cushing’s)

        • Symptoms: abdominal weight gain (truncal obesity), facial fullness (moon facies), decreased libido, easy bruising, menstrual irregularity, high blood pressure (hypertension), excessive hair growth (hirsutism), acne, mood disorders, muscle weakness, high blood sugars (diabetes), osteopenia/osteoporosis 

    • Mineralocorticoid (aldosterone) – “salt hormone”

      • Deficiency from primary adrenal insufficiency, CAH, medications and cause

        • Primary Aldosterone deficiency

        • Symptoms: increased pigmentation in skin and mucosa (palm creases, axillary region, scars darken), salt craving, fatigue/malaise

      • Excess production is due to adenoma, hyperplasia and familial genetics causing

        • Conn’s syndrome or Primary hyperaldosteronism

        • Symptoms: muscle weakness, cramping, headache, fatigue, palpitation, excessive urination (polyuria), high blood pressure (hypertension)

    • Androgens (DHEA) produced are weak steroids or steroid precursors of sex hormones

  • Adrenal Medulla produces

    • Catecholamines that cause general physiological changes that prepare the body for physical activity

    • These catecholamines are responsible for day to day survival.

    • Three types of catecholamines are

      • Adrenaline (epinephrine), Noradrenaline (norepinephrin), and Dopamine

    • Deficiency cannot occur, as this would result to death

    • Excess can occur in setting of genetic mutations or  tumors

      • Genetic mutation: MEN2, VHL, NF1

      • Tumor: Pheochromocytoma

      • Symptoms: headache, sweating, heart racing (palpitations, resting tachycardia), irregular heart rate (arrhythmia), pale (pallor), anxiety, nausea, fatigue, epigastric pain, high blood pressure (hypertension), postural hypotension, fever, tremor.