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.

The hormones of the pituitary have different actions in the body, and the symptoms of hypopituitarism therefore depend on which hormone is deficient. The symptoms may be subtle and are often initially attributed to other causes. In most of the cases, three or more hormones are deficient. The most common problem is insufficiency of follicle-stimulating hormone (FSH) and/or luteinizing hormone (LH) leading to sex hormone abnormalities. Growth hormone deficiency is more common in people with an underlying tumor than those with other causes.

Sometimes, there are additional symptoms that arise from the underlying cause; for instance, if the hypopituitarism is due to a growth hormone-producing tumor, there may be symptoms of acromegaly (enlargement of the hands and feet, coarse facial features), and if the tumor extends to the optic nerve or optic chiasm, there may be visual field defects. Headaches may also accompany pituitary tumors, as well as pituitary apoplexy (infarction or haemorrhage of a pituitary tumor) and lymphocytic hypophysitis (autoimmune inflammation of the pituitary). Apoplexy, in addition to sudden headaches and rapidly worsening visual loss, may also be associated with double vision that results from compression of the nerves in the adjacent cavernous sinus that control the eye muscles.

Pituitary failure results in many changes in the skin, hair and nails as a result of the absence of pituitary hormone action on these sites.

The symptoms due to a prolactinoma are broadly divided into those that are caused by increased prolactin levels or mass effect.

Those that are caused by increased prolactin levels are:

- Amenorrhea (disappearance of ovulation periods)

- Galactorrhea (Milk production; infrequent in men)

- Loss of axillary and pubic hair

- Hypogonadism (Reduced function of the gonads.)

- Gynecomastia (an increase in male breast size)

- Erectile dysfunction (in males)

Those that are caused by mass effect are:

- Bitemporal hemianopsia (due to pressure on the optic chiasm)

- Vertigo

- Nausea, vomiting

The various signs and symptoms in Sheehan's syndrome are caused by damage to the pituitary, which causes a decrease in one or more hormones it normally secretes (see Pathophysiology section). Since the pituitary controls many glands in the endocrine system, partial or complete loss of a variety of functions may result.

Most common initial symptoms of Sheehan's syndrome are agalactorrhea (absence of lactation) and/or difficulties with lactation. Many women also report amenorrhea or oligomenorrhea after delivery. In some cases, a woman with Sheehan syndrome might be relatively asymptomatic, and the diagnosis is not made until years later, with features of hypopituitarism. Such features include secondary hypothyroidism with tiredness, intolerance to cold, constipation, weight gain, hair loss and slowed thinking, as well as a slowed heart rate and low blood pressure. Another such feature is secondary adrenal insufficiency, which, in the rather chronic case is similar to Addison's disease with symptoms including fatigue, weight loss, hypoglycemia (low blood sugar levels), anemia and hyponatremia (low sodium levels). Such a woman may, however, become acutely exacerbated when her body is stressed by, for example, a severe infection or surgery years after her delivery, a condition equivalent with an Addisonian crisis. The symptoms of adrenal crisis should be treated immediately and can be life-threatening. Gonadotropin deficiency will often cause amenorrhea, oligomenorrhea, hot flashes, or decreased libido. Growth hormone deficiency causes many vague symptoms including fatigue and decreased muscle mass.

Uncommonly, Sheehan syndrome may also appear acutely after delivery, mainly by hyponatremia. There are several possible mechanisms by which hypopituitarism can result in hyponatremia, including decreased free-water clearance by hypothyroidism, direct syndrome of inappropriate antidiuretic hormone (ADH) hypersecretion, decreased free-water clearance by glucocorticoid deficiency (independent of ADH). The potassium level in these situations is normal, because adrenal production of aldosterone is not dependent on the pituitary.

Symptoms caused by hormone excess and associated mass effects include:

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

The cause of hyperpituitarism in most cases is due to pituitary adenomas. They usually come from the anterior lobe, are functional and secrete the hormone, GH and prolactin.

In women, a high blood level of prolactin often causes hypoestrogenism with anovulatory infertility and a decrease in menstruation. In some women, menstruation may disappear altogether (amenorrhoea). In others, menstruation may become irregular or menstrual flow may change. Women who are not pregnant or nursing may begin producing breast milk. Some women may experience a loss of libido (interest in sex) and breast pain, especially when prolactin levels begin to rise for the first time, as the hormone promotes tissue changes in the breast. Intercourse may become difficult or painful because of vaginal dryness.

In men, the most common symptoms of hyperprolactinaemia are decreased libido, sexual dysfunction (in both men and women), erectile dysfunction, infertility, and gynecomastia. Because men have no reliable indicator such as menstruation to signal a problem, many men with hyperprolactinaemia being caused by a pituitary adenoma may delay going to the doctor until they have headaches or eye problems caused by the enlarged pituitary pressing against the adjacent optic chiasm. They may not recognize a gradual loss of sexual function or libido. Only after treatment do some men realize they had a problem with sexual function.

Because of hypoestrogenism and hypoandrogenism, hyperprolactinaemia can lead to osteoporosis.

A prolactinoma is a benign tumor (adenoma) of the pituitary gland that produces a hormone called prolactin. It is the most common type of functioning pituitary tumor. Symptoms of prolactinoma are too much prolactin in the blood (hyperprolactinemia), or those caused by pressure of the tumor on surrounding tissues.

Prolactin stimulates the breast to produce milk, and has many other functions such as regulation of mood. Hence prolactin levels are usually higher during pregnancy and after childbirth. After delivery of a baby, a mother's prolactin levels come down to normal a few weeks after breastfeeding is discontinued. Each time the milk is dispensed, prolactin levels rise; this process may cycle to maintain milk production. In males it is responsible for the sexual refractory period after orgasm and excess levels can lead to erectile dysfunction.

Based on size, a prolactinoma can be classified as a "microprolactinoma" (10 mm diameter).

The symptoms of Cushing's disease are similar to those seen in other causes of Cushing's syndrome.

Patients with Cushing's disease usually present with one or more signs and symptoms secondary to the presence of excess cortisol or ACTH.

Although uncommon, some patients with Cushing's disease have large pituitary tumors (macroadenomas). In addition to the severe hormonal effects related to increased blood cortisol levels, the large tumor can compress adjacent structures. These tumors can compress the nerves that carry information from the eyes, causing a decrease in peripheral vision. Glaucoma and cataracts also may occur in Cushing's syndrome. In children, the two main symptoms are obesity and decreased linear growth.

The clinical diagnosis must be based on the presence of one or more of the symptoms listed below, because the syndrome itself has no true pathognomonic signs or symptoms. The most common symptoms seen in male patients are purple striae, muscle atrophy, osteoporosis, and kidney stones.

The syndrome can present with variable symptoms, even between members of the same family harboring the same mutation. Typically most or all tissues are resistant to thyroid hormone, so despite raised measures of serum thyroid hormone the individual may appear euthyroid (have no symptoms of over- or underactivity of the thyroid gland). The most common symptoms are goiter and tachycardia. It has also been linked to some cases of attention deficit hyperactivity disorder (ADHD), although the majority of people with that diagnosis have no thyroid problems.

An association with depression has been proposed.

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

Sheehan's syndrome, also known as postpartum pituitary gland necrosis, is hypopituitarism (decreased functioning of the pituitary gland), caused by ischemic necrosis due to blood loss and hypovolemic shock during and after childbirth.

Hyperprolactinaemia may be caused by either disinhibition (e.g., compression of the pituitary stalk or reduced dopamine levels) or excess production from a prolactinoma (a type of pituitary adenoma). A blood serum prolactin level of 1000–5000 mIU/L could be from either mechanism, but >5000 mIU/L (>200 µg/L) is likely due to the activity of an adenoma; macroadenomas (large tumours over 10 mm diameter) have levels of prolactin up to 100,000 mIU/L.

Hyperprolactinemia inhibits the secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus (by increasing the release of dopamine from the arcuate nucleus), which in turn inhibits the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary gland and results in diminished gonadal sex hormone production (termed hypogonadism). This is the cause of many of the symptoms described below.

In many people, elevated prolactin levels remain unexplained and may represent a form of hypothalamic–pituitary–adrenal axis dysregulation.

Thyroid hormone resistance (sometimes Refetoff syndrome) describes a rare syndrome in which the thyroid hormone levels are elevated but the thyroid stimulating hormone (TSH) level is not suppressed, or not completely suppressed as would be expected. The first report of the condition appeared in 1967. Essentially this is decreased end organ responsiveness to thyroid hormones. A new term "impaired sensitivity to thyroid hormone" has been suggested in March 2014 by Refetoff et al.

There are three major types of adrenal insufficiency.

- Primary adrenal insufficiency is due to impairment of the adrenal glands.

- 80% are due to an autoimmune disease called Addison's disease or autoimmune adrenalitis.

- One subtype is called idiopathic, meaning of unknown cause.

- Other cases are due to congenital adrenal hyperplasia or an adenoma (tumor) of the adrenal gland.

- Secondary adrenal insufficiency is caused by impairment of the pituitary gland or hypothalamus. Its principal causes include pituitary adenoma (which can suppress production of adrenocorticotropic hormone (ACTH) and lead to adrenal deficiency unless the endogenous hormones are replaced); and Sheehan's syndrome, which is associated with impairment of only the pituitary gland.

- Tertiary adrenal insufficiency is due to hypothalamic disease and a decrease in the release of corticotropin releasing hormone (CRH). Causes can include brain tumors and sudden withdrawal from long-term exogenous steroid use (which is the most common cause overall).

Acromegaly is a disorder that results from excess growth hormone (GH) after the growth plates have closed. The initial symptom is typically enlargement of the hands and feet. There may also be enlargement of the forehead, jaw, and nose. Other symptoms may include joint pain, thicker skin, deepening of the voice, headaches, and problems with vision. Complications of the disease may include type 2 diabetes, sleep apnea, and high blood pressure.

Acromegaly is typically due to the pituitary gland producing too much growth hormone. In more than 95% of cases the excess production is due to a benign tumor, known as a pituitary adenoma. The condition is not inherited from a person's parents. Rarely acromegaly is due to tumors in other parts of the body. Diagnosis is by measuring growth hormone after a person has drunk glucose or by measuring insulin-like growth factor I in the blood. After diagnosis, medical imaging of the pituitary is carried out to look for an adenoma. If excess growth hormone is produced during childhood the result is gigantism.

Treatment options include surgery to remove the tumor, medications, and radiation therapy. Surgery is usually the preferred treatment and is most effective when the tumor is smaller. In those in whom surgery is not effective, medications of the somatostatin analogue or GH receptor antagonist type may be used. The effects of radiation therapy are more gradual than that of surgery or medication. Without treatment those affected live on average 10 years less; however, with treatment life expectancy is typically normal.

Acromegaly affects about 6 per 100,000 people. It is most commonly diagnosed in middle age. Males and females are affected with equal frequency. The first medical description of the disorder occurred in 1772 by Nicolas Saucerotte. The term is from Greek "akron" meaning "extremity" and "mega" meaning "large".

Symptoms include rapid weight gain, particularly of the trunk and face with sparing of the limbs (central obesity). Common signs include the growth of fat pads along the collarbone, on the back of the neck ("buffalo hump" or lipodystrophy), and on the face ("moon face"). Other symptoms include excess sweating, dilation of capillaries, thinning of the skin (which causes easy bruising and dryness, particularly the hands) and mucous membranes, purple or red striae (the weight gain in Cushing's syndrome stretches the skin, which is thin and weakened, causing it to hemorrhage) on the trunk, buttocks, arms, legs, or breasts, proximal muscle weakness (hips, shoulders), and hirsutism (facial male-pattern hair growth), baldness and/or extremely dry and brittle hair. In rare cases, Cushing's can cause hypocalcemia. The excess cortisol may also affect other endocrine systems and cause, for example, insomnia, inhibited aromatase, reduced libido, impotence in men, and amenorrhoea/oligomenorrhea and infertility in women due to elevations in androgens. Studies have also shown that the resultant amenorrhea is due to hypercortisolism, which feeds back onto the hypothalamus resulting in decreased levels of GnRH release.

Cognitive conditions, including memory and attention dysfunctions, as well as depression, are commonly associated with elevated cortisol, and may be early indicators of exogenous or endogenous Cushing's. Depression and anxiety disorders are also common.

Other striking and distressing skin changes that may appear in Cushing's syndrome include facial acne, susceptibility to superficial fungus (dermatophyte and malassezia) infections, and the characteristic purplish, atrophic striae on the abdomen.

Other signs include increased urination (and accompanying increased thirst), persistent high blood pressure (due to cortisol's enhancement of epinephrine's vasoconstrictive effect) and insulin resistance (especially common with ACTH production outside the pituitary), leading to high blood sugar and insulin resistance which can lead to diabetes mellitus. Insulin resistance is accompanied by skin changes such as acanthosis nigricans in the axilla and around the neck, as well as skin tags in the axilla. Untreated Cushing's syndrome can lead to heart disease and increased mortality. Cortisol can also exhibit mineralocorticoid activity in high concentrations, worsening the hypertension and leading to hypokalemia (common in ectopic ACTH secretion). Furthermore, excessive cortisol may lead to gastrointestinal disturbances, opportunistic infections, and impaired wound healing related to cortisol's suppression of the immune and inflammatory responses. Osteoporosis is also an issue in Cushing's syndrome since osteoblast activity is inhibited. Additionally, Cushing's syndrome may cause sore and aching joints, particularly in the hip, shoulders, and lower back. Cushing’s syndrome includes all the causes of increased cortisol leading to the diseased state. Cushing’s disease is a specific type of Cushing’s syndrome caused by a pituitary tumor leading to excessive production of ACTH (adrenocorticotropic hormone). Excessive ACTH stimulates the adrenal cortex to produce high levels of cortisol, producing the disease state. Cushing's disease due to excess ACTH may also result in hyperpigmentation. This is due to Melanocyte-Stimulating Hormone production as a byproduct of ACTH synthesis from Pro-opiomelanocortin (POMC). Alternatively, it is proposed that the high levels of ACTH, β-lipotropin, and γ-lipotropin, which contain weak MSH function, can act on the melanocortin 1 receptor. A variant of Cushing's disease can be caused by ectopic, i.e. extrapituitary, ACTH production from, for example, a small-cell lung cancer. When Cushing's syndrome is caused by an increase of cortisol at the level of the adrenal glands (via an adenoma or hyperplasia), negative feedback ultimately reduces ACTH production in the pituitary. In these cases, ACTH levels remain low and no hyperpigmentation develops. While all Cushing’s disease gives Cushing’s syndrome, not all Cushing’s syndrome is due to Cushing’s disease.

Brain changes such as cerebral atrophy may occur. This atrophy is associated with areas of high glucocorticoid receptor concentrations such as the hippocampus and correlates highly with psychopathological personality changes.

- Rapid weight gain

- Moodiness, irritability, or depression

- Muscle and bone weakness

- Memory and attention dysfunction

- Osteoporosis

- Diabetes mellitus

- Hypertension

- Immune suppression

- Sleep disturbances

- Menstrual disorders such as amenorrhea in women

- Decreased fertility in men

- Hirsutism

- Baldness

- Hypercholesterolemia

Signs and symptoms include: hypoglycemia, dehydration, weight loss, and disorientation. Additional signs and symptoms include weakness, tiredness, dizziness, low blood pressure that falls further when standing (orthostatic hypotension), cardiovascular collapse, muscle aches, nausea, vomiting, and diarrhea. These problems may develop gradually and insidiously. Addison's disease can present with tanning of the skin that may be patchy or even all over the body. Characteristic sites of tanning are skin creases (e.g. of the hands) and the inside of the cheek (buccal mucosa). Goitre and vitiligo may also be present. Eosinophilia may also occur.

People often have few or no symptoms. They may get occasional muscular weakness, muscle spasms, tingling sensations, or excessive urination.

High blood pressure, manifestations of muscle cramps (due to hyperexcitability of neurons secondary to low blood calcium), muscle weakness (due to hypoexcitability of skeletal muscles secondary to hypokalemia), and headaches (due to low blood potassium or high blood pressure) may be seen.

Secondary hyperaldosteronism is often related to decreased cardiac output which is associated with elevated renin levels.

Galactorrhea hyperprolactinemia is increased blood prolactin levels associated with galactorrhea (abnormal milk secretion). It may be caused by such things as certain medications, pituitary disorders and thyroid disorders. The condition can occur in males as well as females. Relatively common etiologies include prolactinoma, medication effect, kidney failure, granulomatous diseases of the pituitary gland, and disorders which interfere with the hypothalamic inhibition of prolactin release. Ectopic (non-pituitary) production of prolactin may also occur. Galactorrhea hyperprolactinemia is listed as a “rare disease” by the Office of Rare Diseases of the National Institutes of Health. This means that it affects less than 200,000 people in the United States population.

Hypothalamic disease is a disorder presenting primarily in the hypothalamus, which may be caused by damage resulting from malnutrition, including anorexia and bulimia eating disorders, genetic disorders, radiation, surgery, head trauma, lesion, tumour or other physical injury to the hypothalamus. The hypothalamus is the control center for several endocrine functions. Endocrine systems controlled by the hypothalamus are regulated by anti-diuretic hormone (ADH), corticotropin-releasing hormone, gonadotropin-releasing hormone, growth hormone-releasing hormone, oxytocin, all of which are secreted by the hypothalamus. Damage to the hypothalamus may impact any of these hormones and the related endocrine systems. Many of these hypothalamic hormones act on the pituitary gland. Hypothalamic disease therefore affects the functioning of the pituitary and the target organs controlled by the pituitary, including the adrenal glands, ovaries and testes, and the thyroid gland.

Numerous dysfunctions manifest as a result of hypothalamic disease. Damage to the hypothalamus may cause disruptions in body temperature regulation, growth, weight, sodium and water balance, milk production, emotions, and sleep cycles. Hypopituitarism, neurogenic diabetes insipidus, tertiary hypothyroidism, and developmental disorders are examples of precipitating conditions caused by hypothalamic disease.

Fortunately, the prognosis for patients with prolactinomas is good: most prolactinomas remain stable or regress. In pregnant women, prolactinomas must be observed closely because the lesions may greatly increase in size.

Gigantism is characterized by an excess of growth hormone (GH). This overproduction of growth hormone that brings about gigantism is virtually always caused by pituitary growths (adenomas). These adenomas are on the anterior pituitary gland. They can also cause overproduction of GH's hypothalamic precursor known as growth hormone releasing hormone (GHRH).

As a result of the excessive amounts of growth hormone, children achieve heights that are well above normal ranges. The specific age of onset for gigantism varies between patients and gender, but the common age that excessive growth symptoms start to appear has been found to be around 13 years. Other health complications may occur in pediatric patients with hyper-secretion of growth hormone such as hypertension. Characteristics more similar to those seen in acromegaly may occur in patients that are closer in age to adolescence since they are nearing growth plate fusion.

Various psychiatric manifestations have been associated with pituitary disorders including pituitary adenomas. Psychiatric symptoms such as depression, anxiety apathy, emotional instability, easy irritability and hostility have been noted.