In the setting of critical illness, the production and function of many hormones can be interrupted. As a result, new endocrine disorders may arise or preexisting endocrine disorders can become exacerbated.
DISORDERS OF THE PITUITARY GLAND
The pituitary gland, or “master gland,” is a small, pea-shaped gland at the base of the brain. The anterior pituitary gland produces the majority of the hormones and is the portion of the gland that is most likely to become dysfunctional. It produces adrenocorticotrophic hormone (ACTH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin, growth hormone (GH), and thyroid-stimulating hormone (TSH).1 The posterior gland is responsible for producing vasopressin, also called antidiuretic hormone (ADH). A lack of vasopressin can lead to diabetes insipidus, or an inability to properly concentrate urine. The posterior gland also produces oxytocin, which helps with uterine contractions.
Most cases of hypopituitarism arise from surgery or radiation, and the rest are associated with tumors of the pituitary itself or extrapituitary tumors. Important considerations of pituitary dysfunction include pituitary dysfunction after transsphenoidal hypophysectomy or craniopharyngioma, apoplexy, and Sheehan syndrome.
In 1.1% of patients with transsphenoidal hypophysectomy or craniopharyngioma resection, a triphasic response of central diabetes insipidus, syndrome of inappropriate ADH secretion (SIADH), and chronic central diabetes insipidus may occur.2 Table 22-1 shows the triphasic phase after transsphenoidal hypophysectomy or craniopharyngioma resection.
TABLE 22-1The Three Phases of the Triphasic Response |Favorite Table|Download (.pdf) TABLE 22-1The Three Phases of the Triphasic Response
|Phase ||Timeframe ||Presentation and Etiology ||Classic Labs |
|First ||Initial 4–5 d ||Central diabetes insipidus due to initial ischemia or trauma to vasopressin-secreting cells of pituitary ||High serum osmolality, low urine osmolality, and potential hypernatremia |
|Second ||Next 1–2 d ||SIADH due to vasopressin leak from damaged cells of posterior pituitary gland ||Low serum osmolality, high urine osmolality, and hyponatremia |
|Third ||Potentially persistent vs resolution after next 5–6 d ||Chronic central diabetes insipidus, provided that 80–90% of the vasopressin-secreting cells have been destroyed ||High serum osmolality, low urine osmolality, and hypernatremia (vs normal labs) |
Apoplexy, or pituitary hemorrhage, may present with a sudden intense headache and visual changes and/or diplopia related to optic nerve compression.3,4 There is often loss of hormones that are secreted from the anterior pituitary gland, including ACTH, resulting in central adrenal insufficiency, with an immediate need for stress-dose steroids, in addition to neurosurgical intervention to decompress the hemorrhagic region.5
Sheehan syndrome is an infarction of the pituitary gland that occurs in pregnancy, typically in the setting of delivery complications (eg, excessive blood loss or severe hypotension).6 Sometimes it can have a subtle presentation and the diagnosis is not made until the mother fails to lactate and/or menstruate postpartum.7 As with pituitary apoplexy, central adrenal insufficiency is the most pressing concern, with a risk ...