Pituitary Hypofunction

Pituitary-Hypothalamic Disease

2 methods of destruction: hormonal and non-hormonal

Hormonal Process

hypersecretion – excessive hormone released by pituitary adenoma

GH – acromegaly

ACTH – Cushing’s disease

Prolactin – amenorrhea/galactorrhea

hyposecretion

Loss of pituitary gland reserve Þ hypopituitarism

Non-Hormonal Process

Effects of expanding mass (enlarged sella turcica)

Suprasella turcica extension Þ optic chiasm compression Þ loss of peripheral vision (bitemporal hemionopsia)

Lateral extension Þ 3^rd, 4^th, 6th cranial nerve compressions Þ extraocular muscle dysfunction. Also, arterial compression

Sphenoid extension to nasopharynx: nasal discharge (Rhinorrhea) of CSF

Hypothalamic extension Þ abnormalities in thirst, appetite, sleep , and temperature

Temporal extension Þ seizures

Extension into 3^rd ventricle Þ obstructive hydrocephalus, Ý intercranial pressure

Effects of underlying disease

Characteristic of underlying disease process

Etiology – "The nine I’s"

(1) Invasive – Pituitary adenomas can grow large enough to cause hypopituitarism (craniopharyngioma)

(2) Infarction – Ischemic damage (cell death due to loss of blood supply)

Sheehan’s syndrome – hypopituitarism resulting from ischemic necrosis in hypotensive post-partum women

(3) Infiltrative: abnormal cells (metastases, granulomas) or substances (Fe+) infiltrate, replace, and destroy hypothalamus and/or pituitary tissues

(4) Injury: Head trauma

(5) Immunologic: Autoimmune destruction (Hasimoto’s thyroiditis, lymphocytic hypophysitis, autoimmune adrenalitis)

(6) Iatrogenic: Physician induced hypopituitarism because of surgery or radiation therapy

(7) Infectious: Tuberculosis, HIV

(8) Idiopathic: "unknown cause"

(9) Isolated: Isolated defect in the secretion of one pituitary hormone

Pituitary Hormone Deficiency – Secondary deficiency

ACTH deficiency – leads to:

(1) Cortisol Deficiency – Addison-like symptoms: anorexia, weight loss, nausea, abd. pain, fatigue, vomiting, fever, hypotension, hypoglycemia, hyponatremia (ß excretion of water, ß tolerance to stress); hyperpigmentation seen in Addison’s disease is absent (NO ACTH); appears in 3-14 days

(2) Androgen Deficiency – in women: loss of axillary and pubic hair (ß androgen)

LH/FSH deficiency – leads to:

Children: gonadal hormone deficiency – delayed puberty, eunuchoid appearance (long arms and legs)

Women: estrogen and androgen deficiency – amenorrhea, loss of libido, infertility, osteoporosis, accelerated atherosclerosis

Men: androgen deficiency – abnormal sexual function, loss of libido, ß muscle strength fatigue

GH deficiency – leads to deficiency of insulin-like growth factor I

Children: growth retardation

Adult: ß muscle mass, ß strength, fatigue, premature atherosclerosis

TSH deficiency – leads to hypothyroidism

fatigue, lethargy, cold intolerance, dry skin, mental apathy, alopecia, constipation, myxedema, pseudomotonia. 2-6 wks

Prolactin deficiency

failure to lactate post-partum

Diagnosis – differentiation of primary from secondary hypfunction

Assessment of target gland function – glands controlled by pituitary will have ß function with pituitary dysfunction

Assess pituitary function – suspect hypothalamic or pituitary disease only if target gland hormone level is low and the corresponding pituitary hormone is NOT elevated (i.e. above normal range)

Dynamic testing – when hypofunction is suspected perform a stimulation test!!!!

Assessment of pituitary hormone reserve

Anatomical assessment – neurologicla exam, radiological studies

Treatment

Replace hormonal defect

Treat the underlying disease