Glossary

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Hemangioblastoma: a benign vascular tumor that is typically cystic and can occur throughout the central nervous system but found most frequently in the cerebellum, spinal cord and brainstem. Primary treatment of symptomatic hemangioblastomas is usually by surgical removal. Von Hippel Lindau syndrome is an autosomal dominant inherited disorder characterized by both benign hemangioblastomas of the central nervous system and retina as well as renal cell carcinoma, pancreatic cysts and tumors and other neuroendocrine tumors.
Hematoma: a collection of blood from abnormal bleeding. Intracranial hematomas may form over the surface of the dura (epidural), under the dura (subdural), under the arachnoid membrane (subarachnoid hemorrhage) or within the brain (intracerebral or intraparenchymal). Hematomas may arise from trauma, bleeding into a tumor, from hypertension, excessive anticoagulation medication or after intracranial surgery. Depending upon the size and location, a hematoma may require evacuation typically through a craniotomy. A chronic subdural hematoma is liquefied and can often be removed through a small hole in the bone and placement of a drainage catheter.
Hydrocephalus: a condition of excessive cerebrospinal fluid (CSF) in the ventricles, or cavities, of the brain. Hydrocephalus may cause increased intracranial pressure inside the skull and progressive enlargement of the head (in children), cognitive impairment and eventually if progressive, stupor and coma. Hydrocephalus is usually due to blockage of CSF outflow in the ventricles or in the subarachnoid space over the brain. It may occur after a brain infection (meningitis), brain hemorrhage or from a tumor compressing the ventricular system. Treatment is often by placing of a ventriculo-peritoneal (VP) shunt or in some case by a 3^rd ventriculostomy.
Hydrocortisone: the pharmacological replacement of the natural stress hormone cortisol; used as an anti-inflammatory in the treatment of allergic reactions and as substitute for cortisol. Learn more.
Hyperprolactinemia: the presence of abnormally high prolactin in the blood. Normal blood prolactin levels are less than 20 – 25 ng/ml. Prolactin secretion is inhibited by dopamine which is also known as prolactin inhibitory factor. Hyperprolactinaemia can result from multiple causes including pregnancy, hypothyroidism (low thyroid), kidney failure, medications, distortion of the pituitary gland and stalk from a tumor (“stalk compression”) and from a prolactinoma. Learn more.
Hypogonadism: a defect of the reproductive system resulting in lack of function of the gonads (ovaries or testes). The gonads have two major functions: to produce hormones (testosterone, estradiol), and to produce gametes (eggs or sperm). Sex hormones deficiency can result in defective primary or secondary sexual development, infertility and loss of libido. Defective egg or sperm development results in infertility. pituitary adenomas and other tumors that impinge upon the pituitary gland can cause hypogonadism (a subset of hypopituitarism) by causing either decreased production of LH and FSH or by causing hyperprolactinemia which inhibits LH and FSH production. Learn more.
Hypophysis: the pituitary gland also referred to as the “master gland” because it controls all hormonal function. The pituitary is located under the brain in the skull base, weighs less than one gram and measures one centimeter in width. Hormones when released by the pituitary into the blood stream have a dramatic and broad range of effects on growth and development, sexuality and reproductive function, metabolism, the response to stress and overall quality of life. Learn more.
Hypophysitis (pituitary inflammation): inflammation of the pituitary gland and often the pituitary stalk. The etiology is uncertain but the results are typically permanent pituitary failure often with diabetes insipidus. Treatment is typically with hormone replacement therapy and high dose glucocorticoids (steroids) to reduce inflammation.
Hypopituitarism: loss of pituitary gland hormonal function which may involve one or more of the hormonal axes (adrenal, thyroid, gonadal, etc). The term refers to both anterior and posterior pituitary gland dysfunction. Hypopituitarism may be temporary or permanent. Complete loss of all pituitary hormonal function is referred to as panhypopituitarsim. Learn more.
Hypothalamus: this critical brain region is immediately below the thalamus and above the pituitary gland. The hypothalamus plays a major role in regulating body temperature, appetite, water balance, blood sugar and metabolism. Most of these functions are exerted through the connection to the pituitary gland by hypothalamic releasing hormones that travel down the pituitary stalk (infundibulum) to the gland.