Glossary

• acromegaly- a chronic illness typically caused by excessive amounts of growth hormone (GH) produced by a pituitary tumor.

• adenoma- A benign tumor. See micro and macroadenoma.

• alopecia- Loss of hair. Several patterns of alopecia are recognized and may include loss of head hair, body hair or patchy loss.

• algorithms- A set of rules or procedures for solving a problem; a number of steps applied for diagnosis and treatment of a specific disease.

• analogue- A manufactured chemical resembling another molecule but with some alterations in structure, conferring additional benefits e.g. longer duration of action than the native molecule.

• anterior/posterior lobe- Pertains to the two parts of the pituitary gland. The anterior (front lobe) and posterior (back lobe) each secrete individual hormones into the blood stream.

• apoplexy- Cerebral hemorrhage. Sudden extensive bleed into an organ or tissue. This may occur in the pituitary gland resulting in acute loss of all hormones synthesized by the pituitary gland.

• benign- With regard to a tumor; nonmalignant, noncancerous

• Bromocriptine- See text.

• Cabergoline- See text.

• colon polyps- Abnormal tissue growths in the colon which may be benign or malignant.

• cerebrospinal fluid (CSF)- A fluid consisting of proteins and electrolytes which nourish and cushion the brain and spinal cord. This fluid circulates within a closed system around the spinal cord and within and around the brain.

• craniotomy- A surgical procedure where an incision is made in the skull bone to gain access to the brain.

• CT scan- CAT scan. Computerized axial tomography.

• debulk- Surgical process to remove most of the tumor mass.

• diabetes insipidus- Deficiency of the posterior pituitary hormone, ADH, resulting in impaired fluid retention by the kidney. This results in excessive urination leading to dehydration.

• diabetes mellitus- A group of diseases characterized by problems with glucose control, usually related to a deficiency of the hormone, insulin, or resistance to its action. This is characterized by high blood sugar (hyperglycemia).

• dopamine- A neurotransmitter (chemical messenger) found in the brain. In the case of the pituitary gland; dopamine passes continuously from the hypothalamus to the anterior pituitary lactotroph cells where it is responsible for continued suppression of prolactin synthesis and secretion.

• ectopic tumors- GH producing tumor found elsewhere in the body other than the pituitary.

• endocrine glands- Ductless glands which produce hormones.

• Endocrinologist- A physician who specializes in the medical care of patients with dysfunction of the endocrine system.

• endoscopy- Internal exploration of the body through use of the endoscope (a flexible tube consisting of glass fibers transmitting light and facilitating vision and photography).

• Gamma Knife Radiosurgery- Highly focused beam of gamma radiation that can pinpoint a particular area while avoiding damage to surrounding tissues and tissues in the path of the radiation. It also produces an effective reduction in GH secretion somewhat faster than traditional radiotherapy.

• gigantism- The childhood version of acromegaly. This condition is the result of excessive secretion of GH from a pituitary tumor. It usually manifests as an increase in linear growth (height) and a delay in puberty.

• growth hormone (GH)- A hormone secreted by the anterior pituitary gland which regulates normal growth and metabolism.

• Growth Hormone Releasing Hormone (GHRH)- A hormone originating from the hypothalamus that stimulates the synthesis and secretion of GH from somatotrophs of the anterior pituitary.

• hormone- A chemical substance (‘messenger’) secreted from an organ or gland which can travel from one cell to another, through the blood or through nerves, to another part of the body. Hormones stimulate the cells of that tissue to perform a specific function. This may involve synthesis of another hormone (‘second messenger’) in the target organ. Hormones may function to stimulate growth of cells, alter their metabolism and stimulate them to synthesize or inhibit the synthesis of new chemicals.

• hypercalciuria- Excessive calcium in the urine.

• hypertension- High blood pressure.

• hypertriglyceridemia- Elevated levels of triglycerides (neutral fats) in the blood. Can lead to cardiovascular disease.

• hypopituitarism- Deficiency or decreased synthesis and secretion of hormones from the pituitary. This may be congenital or may result from pituitary tumor enlargement, pituitary surgery, or pituitary radiation.

• hypothalamus- The hypothalamus is an area of the brain situated above the pituitary. It is composed of several discreet areas termed ‘nuclei’, each with its own function. The hypothalamus secretes several stimulatory and inhibitory hormones that pass down the pituitary stalk and influence the synthesis of anterior pituitary hormones. It also synthesizes hormones which pass down dedicated nerves to be stored in the posterior pituitary gland, from which they are subsequently released.

• Insulin-like growth factor (IGF-1)- A hormone released from the liver following stimulation by growth hormone. This hormone is responsible for carrying out some of the growth and metabolic effects generally included under the heading of GH effects.

• Ischemic stroke- Permanent damage to part of the brain subserved by an artery that becomes occluded, usually by a blood clot.

• lactotrophs- Anterior pituitary cells secreting prolactin (PRL).

• macroadenoma- Large tumor defined as greater than 1cm/10mm in size.

• malocclusion- Misalignment of teeth when attempting to bite. In patients with Acromegaly, the usual problem is a reversal of the normal bite pattern, with the lower teeth biting ahead of the upper teeth.

• meningitis- Inflammation of the membranes (meninges) of the brain and spinal cord usually caused by a viral or bacterial infection.

• microadenoma- Small tumor defined as less than 1cm/10mm in size.

• Magnetic Resonance Imaging (MRI)- A non x-ray imaging technique using magnetic waves.

• necrosis- Cell, tissue or organ death.

• Octreo Scan- Intravenously administered, low dose, radioactive octreotide binds to cells with Somatostatin receptors on their surface. This is used to locate GH secreting cells outside of the pituitary (e.g. ectopic tumors).

• Octreotide- See text...

• Oral Glucose Tolerance Test (OGTT)- Patients are given a 75 gram glucose drink. Blood samples for glucose and GH levels are then drawn at regular intervals (30 minutes over 2 hours).

Normally, growth hormone declines to very low levels when healthy people take the OGTT. However, patients with Acromegaly fail to demonstrate a decline in GH levels during an OGTT and may in fact paradoxically demonstrate an increase in GH levels. This test is used in making the biochemical diagnosis of Acromegaly and is also used when assessing the efficacy of the treatment of Acromegaly.

The OGTT used to be the ‘gold standard’ for defining the presence of diabetes. It is still used in various forms to diagnose the presence of diabetes during pregnancy.

• oligo/amenorrhea- Infrequent/absent menstruation.

• optic chiasm- A crossing over of the nerve fibers from the inner half of each retina (retina-posterior portion of the eye that is responsible for vision. Nerve impulses are generated here and run back to the brain carrying information regarding what is seen.). These fibers carry messages to the visual centers of the brain that record what is being seen in the lateral visual fields. The crossing over of these nerve fibers occurs just above the pituitary gland. Expansion of a pituitary tumor in an upward direction may stretch these nerves and be responsible for loss of vision in the lateral fields.

• Pegvisomant- See text...

• pituitary fossa/sella turcica -‘Turkish saddle.’ Refers to a concavity (bowl-shaped depression) in the sphenoid bone of the skull. The sella turcica houses the pituitary gland.

• pituitary gland (hypophysis)- Pea-sized, endocrine gland attached to the lower surface of the hypothalamus by the pituitary stalk. It is composed of an anterior and posterior lobe and often referred to as the ‘master gland.’ It secretes a number of hormones responsible for many vital body functions.

• prognathism- A protrusion of the jaw as a result of its bony expansion and loss of its angle.

• Prolactin (PRL)- A hormone synthesized in and secreted from the anterior pituitary. Prolactin normally stimulates production of milk during pregnancy.

• renin- An enzyme stimulating the secretion of the hormone aldosterone. Aldosterone is indirectly responsible for several metabolic functions including regulation of electrolytes in the blood, pH, blood volume and blood pressure. Aldosterone is produced in the cortex of the adrenal gland.

• rhinorrea- Leakage of CSF through the nose. This usually originates from a defect (hole) in the floor of the sphenoid sinus following surgery through this area.

• Syndrome of Inappropriate Antidiuretic Hormone secretion (SIADH)- Abnormal secretion of ADH from the posterior pituitary. This may occur following surgery to the pituitary.

• sinusitis- Inflammation or infection of a sinus cavity.

• skin tags- Small, soft outgrowths of skin usually located on the neck, axillae and groin.

• sleep apnea- Numerous, temporary absences of breathing while sleeping, each lasting only a few seconds at a time. This condition results in disturbed sleep patterns, daytime somnolence and elevated blood pressure in the lungs.

• somatic- Pertains to the body, physical aspects

• somatotrophs- Anterior pituitary cells dedicated to the synthesis and secretion of growth hormone.

• somatomammotrophs- Anterior pituitary cells secreting both GH and PRL.

• Somatostatin Release Inhibitory Factor (SRIF)- Otherwise known as Somatostatin, this hormone produced in the hypothalamus, inhibits growth hormone secretion from the anterior pituitary gland. It has the ‘opposite’ effect to the growth hormone releasing hormone (GHRH).

• stones & sludge- In the case of Acromegaly, this refers to the presence of stones and thickened biliary secretions in the gallbladder. This may occur naturally or be a side effect of the use of octreotide or one of the other somatostatin analogs.

• sphenoid sinus- The air cavity within the sphenoid bone located at the base of the skull.

• subcutaneous- Beneath the skin.

• target organ- The tissue or gland to which a hormone or chemical messenger is directed, and in which the hormone exerts its effect.

• transphenoidal surgery- See text.

• tumor- An abnormal mass of cells, benign or malignant. Cell proliferation independent of normal, neighboring tissues.

• visual field- The total field or area visible by the eye while fixed on a given forward point.