Diseases of the Pituitary Gland The anterior pituitary adenohypophysis A tumor growing within or near the gland can cause pressure on the cells causing them to fail Pituitary failure is one of the most difficult diagnoses to make A visible tumor can be classified as a micro adenoma if the tumor is smaller than 10 mm or a macroadenoma if the tumor is 10 mm or larger Individual adenohypophysial hormone deficiencies Corticotrophin ACTH deficiency Causes cortisol deficiency Sometimes is associated only with tiredness and manifests only with illness at times of stress or infection Low levels of ACTH and cortisol are suspicious but not diagnostic without a stimulation test insulin stress test Can also be tested for indirectly using synacthen test or metyrapone Treated with replacement hydrocortisone usually oral Thyrotrophin TSH deficiency cid 127 Weight gain and tiredness due to a fall in BMR Primary thyroid failure is much more common and this diagnosis is made when the TSH is raised TSH deficiency should be suspected in any patient with a low concentration of FT4 if the TSH remains in the reference range Treatment is by replacement of thyroxine oral cid 127 Growth hormone deficiency cid 127 GH deficiency in children causes short stature but adults who develop GH deficiency have a change in metabolism Deficiency needs to be proven by stimulation test insulin induced hypoglycemia Patients with GH deficiency will have a low concentration of circulating IGF1 cid 127 Gonadotrophin LH and FSH deficiency cid 127 Manifest in females with amenorrhea due to lack of ovarian secretion of estrogen In males testosterone deficiency causes loss of libido and sometimes a reduction in the growth of facial hair Treatment for both conditions is identical to the treatment for ovarian failure in women and testicular failure in men Disconnection of the pituitary gland from the hypothalamus by the growing tumor causes a rise in circulating prolactin levels as the lactotrophs are no Prolactin causes galactorrhea in the estrogen primed breast and suppresses GnRH release causing amenorrhea cid 127 Other causes include the administration of dopamine antagonist drugs for other conditions such as travel sickness or psychiatric diseases such as Large non functioning pituitary tumors can produce anterior pituitary hypo function by compressing the pituitary cells against the bone of the sella turcica In patients who are deficient in several hormones the most important one to replace is hydrocortisone Hyperprolactinemia longer inhibited by dopamine schizophrenia Anterior pituitary hypofunction panhypopituitarism Then thyroxine then either estrogen testosterone Prolactin is never replaced Tumor size matters Patients with hypopituitarism should have a pituitary MRI to determine whether the cause is a pituitary tumor Non functioning pituitary adenomas Usually made up of gonadotrophs that fail to secrete their gonadotrophins The posterior pituitary is rarely affected by anterior pituitary tumors but can be damaged by TSS resulting in DI Anterior pituitary hyperfunction hyperpituitarism Cushing s disease Clinical features Specific to a pituitary tumor producing uncontrolled excess quantities of ACTH Total exposure of the body s cells to cortisol slowly rises causing a gradual increase in appetite and weight gain Fat synthesis is promoted over protein synthesis and patients develop muscle weakness Skin heals poorly and wounds can take a long time to heal Stretch marks in the skin which may be red Cushing s syndrome Exposure to excess cortisol from conditions other than a pituitary tumor Can be caused by the patient taking glucocorticoids as a treatment for another e g inflammatory condition Can also be caused by an adrenal adenoma making cortisol autonomously or rarely by a malignant tumor making ectopic ACTH cid 127 Options include surgery to the pituitary itself to try to remove the source of ACTH Treatment of Cushing s disease Radiotherapy can be effective to grow Nelson s syndrome Prolactinomas Bilateral adrenalectomy can be performed this will control the excess cortisol levels but will leave a small chance for the tumor in the pituitary gland cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 Secrete large amounts of prolactin Sex steroid deficiency is an important but often missed clinical feature of a high prolactin production cid 127 Women and some men with gynecomastia will complain of milk production Combination of milk production and amenorrhea in women who are not pregnant is key indicator cid 127 Males develop testosterone deficiency loss of libido Treatment of prolactinomas Trial of dopamine agonists should be used For patients who cannot tolerate dopamine agonists surgery of the pituitary gland and or radiotherapy are options Acromegaly to 2 m or more Tumors of somatotrophs secrete excess GH and in children this causes gigantism because they simply grow faster than normal to reach heights of up In adults in whom the epiphyses of the long bones have fused linear growth in unlikely but other tissues undergo hypertrophy Coarse features prognathic jaw and frontal bossing large hands gaps in the teeth due to jaw growth cid 127 Metabolic effects of increased GH cause increased risk of diabetes hypertension vascular disease Following TSS all the patient s pituitary axes need to be reassessed Thyrotrophinomas TSHomas Extremely rare present with features of hyperthyroidism and failure to suppress the blood TSH level Patients may be thought to have primary thyroid disease Fail to respond to TRH confirms diagnosis The posterior pituitary gland neurohypophysis Excess vasopressin The syndrome of inappropriate antidiuretic hormone hypersecretion SIADH A plasma vasopressin concentration which is inappropriate for the given plasma osmolality cid 127 Most commonly this is not truly a pituitary problem but is caused by an ectopic source of vasopressin Causes hyponatremia Transient SIADH can be caused by pituitary surgery Lack of vasopressin Diabetes insipidus DI Presents as polyuria and polydipsia Can be due to post pituitary surgery Another form of DI is due to the failure of the kidneys to respond to