Hormone secreting pituitary adenomas cause one of several forms of hyperpituitarism. The specifics depend on the type of hormone. Some tumors secrete more than one hormone, the most common combination being GH and prolactin, which present as unexpected bone growth and unexpected lactation (in both men and women).

A patient with pituitary adenoma may present with visual field defects, classically bitemporal hemianopsia. It arises from the compression of the optic nerve by the tumor. The specific area of the visual pathway at which compression by these tumours occurs is at the optic chiasma.

The anatomy of this structure causes pressure on it to produce a defect in the temporal visual field on both sides, a condition called bitemporal hemianopsia. If originating superior to the optic chiasm, more commonly in a craniopharyngioma of the pituitary stalk, the visual field defect will first appear as bitemporal inferior quadrantanopia, if originating inferior to the optic chiasm the visual field defect will first appear as bitemporal superior quadrantanopia. Lateral expansion of a pituitary adenoma can also compress the abducens nerve, causing a lateral rectus palsy.

Also, a pituitary adenoma can cause symptoms of increased intracranial pressure.

Prolactinomas often start to give symptoms especially during pregnancy, when the hormone progesterone increases the tumor's growth rate.

Various types of headaches are common in patients with pituitary adenomas. The adenoma may be the prime causative factor behind the headache or may serve to exacerbate a headache caused by other factors. Amongst the types of headaches experienced are both chronic and episodic migraine, and more uncommonly various unilateral headaches; primary stabbing headache, short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) - another type of stabbing headache characterized by short stabs of pain -, cluster headache, and hemicrania continua (HS).

Non-secreting adenomas can go undetected for an extended time because no obvious abnormalities are seen; the gradual reduction in normal activities due to decreased production of hormones is rather less evident. For example, insufficient adrenocorticotropic hormone means that the adrenal glands will not produce sufficient cortisol, resulting in slow recovery from illness, inflammation and chronic fatigue; insufficient growth hormone in children and adolescents leads to diminished stature but which can have many other explanations.

An ectopic (occurring in an abnormal place) pituitary adenoma is a rare type of tumor which occurs outside of the sella turcica, most often in the sphenoid sinus, suprasellar region, nasopharynx and the cavernous sinuses.

An endocrine gland neoplasm is a neoplasm affecting one or more glands of the endocrine system.

Examples include:

- Adrenal tumor

- Pituitary adenoma

The most common form is thyroid cancer.

Condition such as pancreatic cancer or ovarian cancer can be considered endocrine tumors, or classified under other systems.

Pinealoma is often grouped with brain tumors because of its location.

Pituitary tumors occur in 15 to 42% of MEN 1 patients. From 25 to 90% are prolactinomas. About 25% of pituitary tumors secrete growth hormone or growth hormone and prolactin. Excess prolactin may cause galactorrhea (see Pituitary Disorders: Galactorrhea), and excess growth hormone causes acromegaly clinically indistinguishable from sporadically occurring acromegaly. About 3% of tumors secrete ACTH, producing Cushing's disease. Most of the remainder are nonfunctional. Local tumor expansion may cause visual disturbance, headache, and hypopituitarism. Pituitary tumors in MEN 1 patients appear to be larger and behave more aggressively than sporadic pituitary tumors.

Pancreatic islet cell tumors occur in 60 to 70% of patients. Tumors are usually multicentric. Multiple adenomas or diffuse islet cell hyperplasia commonly occurs; such tumors may arise from the small bowel rather than the pancreas. About 30% of tumors are malignant and have local or distant metastases. Malignant islet cell tumors due to MEN 1 syndrome often have a more benign course than do sporadically occurring malignant islet cell tumors.About 40% of islet cell tumors originate from a β-cell, secrete insulin (insulinoma), and can cause fasting hypoglycemia. β-cell tumors are more common in patients 40 years of age. Non-β-cell tumors are somewhat more likely to be malignant.

Most islet cell tumors secrete pancreatic polypeptide, the clinical significance of which is unknown. Gastrin is secreted by many non–β-cell tumors (increased gastrin secretion in MEN 1 also often originates from the duodenum). Increased gastrin secretion increases gastric acid, which may inactivate pancreatic lipase, leading to diarrhea and steatorrhea. Increased gastrin secretion also leads to peptic ulcers in > 50% of MEN 1 patients. Usually the ulcers are multiple or atypical in location, and often bleed, perforate, or become obstructed. Peptic ulcer disease may be intractable and complicated. Among patients presenting with Zollinger-Ellison syndrome, 20 to 60% have MEN 1.

A severe secretory diarrhea can develop and cause fluid and electrolyte depletion with non–β-cell tumors. This complex, referred to as the watery diarrhea, hypokalemia and achlorhydria syndrome (VIPoma) has been ascribed to vasoactive intestinal polypeptide, although other intestinal hormones or secretagogues (including prostaglandins) may contribute. Hypersecretion of glucagon, somatostatin, chromogranin, or calcitonin, ectopic secretion of ACTH resulting in Cushing's syndrome, and hypersecretion of somatotropin–releasing hormone (causing acromegaly) sometimes occur in non–β-cell tumors. All of these are rare in MEN 1.Nonfunctioning pancreatic tumors also occur in patients with MEN 1 and may be the most common type of pancreatoduodenal tumor in MEN 1. The size of the nonfunctioning tumor correlates with risk of metastasis and death.

An adenoma of a parathyroid gland may secrete inappropriately high amounts of parathyroid hormone and thereby cause primary hyperparathyroidism.

They are classified by histology as benign; however, as with many brain tumors, their treatment can be difficult, and significant morbidities are associated with both the tumor and treatment.

- Headache (obstructive hydrocephalus)

- Hypersomnia

- Myxedema

- post surgical weight gain

- Polydipsia

- Polyuria (diabetes insipidus)

- Vision loss (bitemporal hemianopia)

- Vomiting

- often occurs post treatment

- Growth hormone (GH) insufficiency, caused by the reduction in growth hormone (GH) production. Symptoms include:

- Stunted growth and delayed puberty (in children)

- General fatigue, loss of muscle mass and tone (in adults)

- Pituitary insufficiency

- often occurs to some degree because craniopharyngiomas develop in the area of the pituitary stalk, which can affect the function of the pituitary gland.

- Reduction in prolactin production. This is very uncommon and occurs with severe pituitary insufficiency.

- Large pituitary tumors can paradoxically elevate blood prolactin levels due to the "stalk effect." This elevation occurs as a result of the compression of the pituitary stalk, which interferes with the brain's control of prolactin production.

- In premenopausal women, elevated prolactin can lead to reduction or loss of menstrual periods and/or breast milk production (galactorrhea).

- With stalk effect, prolactin levels are usually only slightly elevated, as opposed to prolactinomas in which the prolactin level is usually very high.

- Diabetes insipidus. This occurs due to the absence of a posterior pituitary hormone called antidiuretic hormone (ADH). Symptoms include:

- Excessive thirst

- Excessive urination

- Adrenal insufficiency. This occurs because of a reduction in ACTH production, a reduction in cortisol. In severe cases, it can be fatal. Symptoms include:

- Fatigue

- Low blood pressure

- Electrolyte abnormalities

Pituitary adenomas are seen in 10% of neurological patients. A lot of them remain undiagnosed. Treatment is usually surgical, to which patients generally respond well. The most common subtype, prolactinoma, is seen more often in women, and is frequently diagnosed during pregnancy as the hormone progesterone increases its growth. Medical therapy with cabergoline or bromocriptine generally suppresses prolactinomas; progesterone antagonist therapy has not proven to be successful.

The common symptoms include:

- hyper-pigmentation of the skin

- visual disturbances

- headaches

- abnormal high levels of beta-MSH and ACTH

- abnormal enlargements of the pituitary gland,

- interruption of menstrual cycles in women

Hyperpituitarism is a condition due to the primary hypersecretion of pituitary hormones, it typically results from a pituitary adenoma. Children with hyperpituitarism is rare, disruption of growth regulation, either because of hormone hypersecretion or because of manifestations caused by local compression of the adenoma can occur.

Often these abnormal growths of thyroid tissue are located at the edge of the thyroid gland and can be felt as a lump in the throat. When they are large, they can sometimes be seen as a lump in the front of the neck.

Sometimes a thyroid nodule presents as a fluid-filled cavity called a thyroid cyst. Often, solid components are mixed with the fluid. Thyroid cysts most commonly result from degenerating thyroid adenomas, which are benign, but they occasionally contain malignant solid components.

Symptoms caused by hormone excess and associated mass effects include:

Craniopharyngioma is a rare, usually suprasellar neoplasm, which may be cystic, that develops from nests of epithelium derived from Rathke's pouch. Rathke's pouch is an embryonic precursor of the anterior pituitary.

Craniopharyngiomas are typically very slow growing tumors. They arise from the cells along the pituitary stalk, specifically from nests of odontogenic (tooth-forming) epithelium within the suprasellar/diencephalic region and, therefore, contain deposits of calcium that are evident on an x-ray.

Thyroid nodules are nodules (raised areas of tissue or fluid) which commonly arise within an otherwise normal thyroid gland. They may be hyperplasia or a thyroid neoplasm, but only a small percentage of the latter are thyroid cancers. Small, asymptomatic nodules are common, and many people who have them are unaware of them. But nodules that grow larger or produce symptoms may eventually need medical care. Goitres may have nodules or be diffuse.

Features that result from high level of GH or expanding tumor include:

- Soft tissue swelling visibly resulting in enlargement of the hands, feet, nose, lips and ears, and a general thickening of the skin

- Soft tissue swelling of internal organs, notably the heart with attendant weakening of its muscularity, and the kidneys, also the vocal cords resulting in a characteristic thick, deep voice and slowing of speech

- Generalized expansion of the skull at the fontanelle

- Pronounced brow protrusion, often with ocular distension (frontal bossing)

- Pronounced lower jaw protrusion (prognathism) with attendant macroglossia (enlargement of the tongue) and teeth spacing

- Hypertrichosis, hyperpigmentation and hyperhidrosis may occur in these patients.

- Acrochordon (skin tags)

- Carpal tunnel syndrome

Salivary gland oncocytomas are most common in ages 70–80, females, the parotid gland (85–90%), and are firm, slowly growing, painless masses of less than 4 cm. They may be bilateral.

The signs and symptoms are similar to other malignant salivary gland tumours; however, it may have been preceded by an appreciable mass that was long-standing and did not appear to be growing.

Findings that suggest a malignant salivary gland tumour include rapid growth, facial weakness (due to facial nerve compression), pain, skin ulceration, fixation of the mastoid tip

and parasthesias.

The less-common signs and symptoms of Cushing's disease include the following:

- insomnia

- recurrent infection

- thin skin and stretch marks

- easy bruising

- weak bones

- acne

- balding (women)

- depression

- hip and shoulder weakness

- swelling of feet/legs

- diabetes mellitus

- erectile dysfunction

An oncocytoma is a tumor made up of oncocytes, epithelial cells characterized by an excessive amount of mitochondria, resulting in an abundant acidophilic, granular cytoplasm. The cells and the tumor that they compose are often benign but sometimes may be premalignant or malignant.

Common signs and symptoms of Cushing's disease include the following:

- weight gain

- high blood pressure

- poor short-term memory

- irritability

- excess hair growth (women)

- Impaired immunological function

- red, ruddy face

- extra fat around neck

- moon face

- fatigue

- red stretch marks

- poor concentration

- irregular menstruation

Pituicytoma is a rare brain tumor. It grows at the base of the brain from the pituitary gland. This tumor is thought to be derived from the parenchymal cells of the posterior lobe of the pituitary gland, called pituicytes. Some researchers believe that they arise from the folliculostellate cells in the anterior lobe of the pituitary. As such, it is a low-grade glioma. It occurs in adults and symptoms include visual disturbance and endocrine dysfunction. They are often mistaken for pituitary adenomas which have a similar presentation and occur in the same location. The treatment consists of surgical resection, which is curative in most cases.

Carcinoma ex pleomorphic adenoma, abbreviated ca ex PA, is a type of cancer typically found in the parotid gland. It arises from the benign tumour pleomorphic adenoma.

Its prognosis depends on the stage. Early tumour have essentially a benign behaviour.

Due to the diverse nature of salivary gland tumours, many different terms and classification systems have been used. Perhaps the most widely used currently is that system proposed by the World Health Organization in 2004, which classifies salivary neoplasms as primary or secondary, benign or malignant, and also by tissue of origin. This system defines five broad categories of salivary gland neoplasms:

Benign epithelial tumors

- Pleomorphic adenoma

- Warthin's tumor

- Myoepithelioma

- Basal cell adenoma

- Oncocytoma

- Canalicular adenoma

- Lymphadenoma

- "Sebaceous lymphadenoma"

- "Nonsebaceous lymphadenoma"

- Ductal papilloma

- "Inverted ductal papilloma"

- "Intraductal papilloma"

- "Sialadenoma papilliferum"

- Cystadenoma

- Malignant epithelial tumors

- Acinic cell carcinoma

- Mucoepidermoid carcinoma

- Adenoid cystic carcinoma

- Polymorphous low-grade adenocarcinoma

- Epithelial-myoepithelial carcinoma

- Clear cell carcinoma, not otherwise specified

- Basal cell adenocarcinoma

- Sebaceous carcinoma

- Sebaceous lymphadenocarcinoma

- Cystadenocarcinoma

- Low-grade cribriform cystadenocarcinoma

- Mucinous adenocarcinoma

- Oncocytic carcinoma

- Salivary duct carcinoma

- Salivary duct carcinoma, not otherwise specified

- Adenocarcinoma, not otherwise specified

- Myoepithelial carcinoma

- Carcinoma ex pleomorphic adenoma

- Mammary analogue secretory carcinoma

- Carcinosarcoma

- Metastasizing pleomorphic adenoma

- Squamous cell carcinoma

- Large cell carcinoma

- Lymphoepithelial carcinoma

- Sialoblastoma

- Soft tissue tumors

- Hemangioma

- Hematolymphoid tumors

- Hodgkin lymphoma

- Diffuse large B-cell lymphoma

- Extranodal marginal zone B cell lymphoma

- Secondary tumors (i.e. a tumor which has metastasized to the salivary gland from a distant location)

Others, not included in the WHO classification above, include:

- Intraosseous (central) salivary gland tumors

- Hybrid tumors (i.e. a tumor displaying combined forms of histologic tumor types)

- Hybrid carcinoma

- Others

- Others

- Keratocystoma

- Sialolipoma

Deficiency of all anterior pituitary hormones is more common than individual hormone deficiency.

Deficiency of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), together referred to as the gonadotropins, leads to different symptoms in men and women. Women experience oligo- or amenorrhea (infrequent/light or absent menstrual periods respectively) and infertility. Men lose facial, scrotal and trunk hair, as well as suffering decreased muscle mass and anemia. Both sexes may experience a decrease in libido and loss of sexual function, and have an increased risk of osteoporosis (bone fragility). Lack of LH/FSH in children is associated with delayed puberty.

Growth hormone (GH) deficiency leads to a decrease in muscle mass, central obesity (increase in body fat around the waist) and impaired attention and memory. Children experience growth retardation and short stature.

Adrenocorticotropic hormone (ACTH) deficiency leads to adrenal insufficiency, a lack of production of glucocorticoids such as cortisol by the adrenal gland. If the problem is chronic, symptoms consist of fatigue, weight loss, failure to thrive (in children), delayed puberty (in adolescents), hypoglycemia (low blood sugar levels), anemia and hyponatremia (low sodium levels). If the onset is abrupt, collapse, shock and vomiting may occur. ACTH deficiency is highly similar to primary Addison's disease, which is cortisol deficiency as the result of direct damage to the adrenal glands; the latter form, however, often leads to hyperpigmentation of the skin, which does not occur in ACTH deficiency.

Thyroid-stimulating hormone (TSH) deficiency leads to hypothyroidism (lack of production of thyroxine (T4) and triiodothyronine (T3) in the thyroid). Typical symptoms are tiredness, intolerance to cold, constipation, weight gain, hair loss and slowed thinking, as well as a slowed heart rate and low blood pressure. In children, hypothyroidism leads to delayed growth and in extreme inborn forms to a syndrome called "cretinism".

Prolactin (PRL) plays a role in breastfeeding, and inability to breastfeed may point at abnormally low prolactin levels.

Common causes include bilateral adrenalectomy for the treatment of Cushing's disease, and hypopituitarism. The onset of the disease can occur up to 24 years after a bilateral adrenalectomy has been performed, with an average of up to 15 years after. A preventative measure that can be utilized is prophylactic radiotherapy when a bilateral adrenalectomy is being performed in order to prevent Nelson's syndrome from manifesting. Screening can also be done with the help or an MRI in order to visualize the pituitary for tumors. If tumors are not present then an MRI should be performed at intervals. Hyper-pigmentation and fasting ACTH levels within plasma above 154 pmol/l are predictive of Nelson's syndrome after an adrenalectomy. Risk factors include being younger in age and pregnancy.