Info
🌱 來自: Huppert’s Notes
Anterior Pituitary🚧 施工中
Anterior Pituitary
Hypopituitarism
• Etiologies:
- Impaired synthesis or secretion of one or more hormones; can be primary or secondary (process impairs hypothalamic hormones, with resultant pituitary failure)
- Primary: Traumatic (e.g., head injury), neoplastic (e.g., adenoma), infiltrative/inflammatory (e.g., sarcoidosis), vascular (e.g., sickle cell disease, pregnancy-related), infections (e.g., histoplasmosis, TB), development/structural (e.g., dysplasia)
- Secondary: Hypothalamic dysfunction or stalk interruption due to aforementioned processes
• Clinical features: Depends on which hormones are lost and the extent and duration of deficiency
• Hormone deficiencies:
- ↓ Growth hormone (GH): Fatigue, increased fat mass, decreased muscle mass, growth retardation (children). Clinically this is measured using GH suppression testing with oral glucose tolerance and finding an elevated IGF-1.
- ↓ Luteinizing hormone (LH)/follicle-stimulating hormone (FSH): Hypogonadotropic hypogonadism (infertility, amenorrhea, impotence)
- ↓ Thyroid-stimulating hormone (TSH): Hypothyroidism, growth retardation (children)
- ↓ Adrenocorticotropic hormone (ACTH): Secondary adrenal insufficiency (hypocortisolism; relative preservation of mineralocorticoid production)
- ↓ Prolactin: Inability to lactate
• Diagnosis: Get pituitary MRI. Typically there are low levels of anterior pituitary hormones and thus low levels of target-organ hormones (e.g., low TSH, low free T4). Pearl: Hormone levels that are within normal lab ranges may be “inappropriately normal” based on the clinical context. For example, if free T4 is very low, then a normal TSH level would be inappropriately normal, since in this setting TSH should be elevated.
• Treatment: Replace deficient hormones. Adrenal insufficiency and hypothyroidism are the most important to treat. Patients in need of glucocorticoid replacement require careful dose adjustment in times of stress (e.g., acute illness).
Pituitary Tumors
• Approach:
- Is there mass effect?
- Is the tumor causing hormone excesses or deficiencies? Assess clinically for syndromes of cortisol, prolactin, growth hormone, and thyroid excess or deficiency and test accordingly
- Is the tumor likely to grow and cause problematic mass effect? Obtain MRI brain and repeat over time as needed (interval time to repeat study determined by tumor size)
• Differential diagnosis:
- Pituitary adenomas (can occur as part of MEN1 syndrome – See Table 5.1)
TABLE 5.1 • Multiple Endocrine Neoplasia (MEN) Syndromes
• Microadenomas: <1 cm, incidentally found in approximately 10% of patients with brain MRIs
• Macroadenomas: ≥1 cm
- Rathke cleft cysts
- Craniopharyngiomas
- Meningiomas
- Metastatic disease
• Symptoms:
- Can cause mass effect: Headache, visual changes (optic chiasm compression can lead to bitemporal hemianopia)
- Can cause hypopituitarism and DECREASED hormone levels (see hypopituitarism section above)
- Tumors can also be functional and cause INCREASED hormone levels:
• ↑Prolactin (most common): Hyperprolactinemia
- Symptoms: Hypogonadism (due to inhibition of GnRH) leading to amenorrhea, decreased libido, infertility, galactorrhea
- Diagnosis: Elevated prolactin (>200–250 ng/mL strongly suggests prolactinoma)
- Differential diagnosis: Physiologic hypersecretion (e.g., pregnancy), drug-induced (e.g., antipsychotics), primary hypothyroidism, systemic disorders (e.g., renal failure, cirrhosis), compression of the pituitary stalk (with resultant disruption of dopamine inhibition), secretory pituitary tumor (obtain pituitary MRI to evaluate for tumor)
- Treatment:
• If asymptomatic and microadenoma: Treatment isn’t always necessary and can follow with brain MRIs
• If symptoms or macroadenoma: Dopamine agonists (bromocriptine/cabergoline; caution in patients on antipsychotic medications), typically surgery is NOT needed unless medical management is inadequate to control symptoms
• ↑Growth hormone: Acromegaly
- Symptoms: Large jaw/hands/feet/tongue, frontal bossing, cardiomegaly
- Diagnosis: Elevated IGF-1 (oral glucose tolerance test to confirm) followed by pituitary MRI
- Treatment:
• Surgery (transsphenoidal tumor resection) or radiation
• Dopamine agonists (e.g., somatostatin analogues)
• Pegvisomant (GH receptor antagonist) can be used if surgery or radiation are not possible
• ↑ TSH: Very rare – see “hyperthyroidism” in later section
• ↑ACTH: Cushing’s disease
- Definition: Excess ACTH secretion from pituitary tumor = Cushing disease, which is the most common cause of Cushing syndrome (refers to hypercortisolism regardless of cause)
- Symptoms: Proximal muscle weakness, facial plethora, wasting of the extremities with increased fat in the abdomen and face, wide purplish striae, bruising with no obvious trauma, dorsocervical and supraclavicular fat pads, DM2 due to insulin resistance, neuropsychiatric symptoms
- Diagnosis:
• Step 1: Establish whether the patient has hypercortisolism: Late-night salivary cortisol, 24-hour urinary free cortisol excretion, or overnight 1 mg dexamethasone suppression test
• Step 2: Differentiate ACTH-dependent from ACTH-independent Cushing syndrome by measuring ACTH
- If ACTH is low (ACTH-independent), it is typically due to a cortisol-secreting adrenal adenoma, adrenal carcinoma, or bilateral multi-nodular adrenal hyperplasia. Get a CT adrenal protocol to evaluate the adrenal glands
- If ACTH is high (ACTH-dependent), it is typically due to a pituitary adenoma. Get a pituitary MRI followed by petrosal sinus sampling as appropriate
- Treatment: For Cushing’s disease from a pituitary adenoma, consider surgery (transsphenoidal resection of the involved pituitary)