Cushing's syndrome

Cushing's syndrome is a systemic endocrine disorder caused by prolonged exposure to supraphysiological levels of glucocorticoids, whether from exogenous administration or endogenous overproduction.[1][2] The most common cause is exogenous glucocorticoid use; among endogenous causes, corticotropin (ACTH)-secreting pituitary adenomas (Cushing's disease) account for 60–70% of cases, followed by cortisol-producing adrenal tumors (20–30%) and ectopic ACTH-secreting neuroendocrine tumors (6–10%).[1] Chronic hypercortisolism produces multisystem morbidity including metabolic derangement, skeletal fragility, immunosuppression, and characteristic changes in body habitus.[2][3] In the oral and maxillofacial region, the condition manifests primarily through glucocorticoid-induced osteoporotic changes in the jaws, impaired wound healing, increased susceptibility to oral infections, and mucosal hyperpigmentation in ACTH-dependent forms.[4][5] Dental radiographic findings are those of generalized osteopenia rather than a discrete focal lesion. Management is directed at the underlying cause of hypercortisolism, with dental professionals playing a role in recognizing jaw and oral soft-tissue changes that may prompt referral.

The condition is named after Harvey Cushing, who described the clinical constellation in 1932.[3] Current terminology distinguishes:

• Cushing's syndrome — the umbrella term for any cause of chronic glucocorticoid excess, whether exogenous or endogenous.[1][2]
• Cushing's disease — specifically denotes ACTH-dependent hypercortisolism caused by a pituitary corticotroph adenoma.[1]
• Ectopic Cushing's syndrome — hypercortisolism driven by a non-pituitary ACTH-secreting tumor.[1]
• Exogenous (iatrogenic) Cushing's syndrome — caused by therapeutic glucocorticoid administration via any route.[1]
• Pseudo-Cushing's syndrome (nonneoplastic hypercortisolism) — mild cortisol elevation associated with obesity, alcoholism, depression, or polycystic ovary syndrome, without a neoplastic source.[1][4]

The older term "hypercortisolism" remains in clinical use as a synonym for the biochemical state underlying all forms.

• Incidence: Endogenous Cushing's syndrome is rare, estimated at 2–8 per million per year. Exogenous Cushing's syndrome is far more common but its true prevalence is difficult to quantify.[1][2]
• Sex: Endogenous forms show a female predominance of approximately 3:1.[3]
• Age: Peak incidence occurs in the fourth to sixth decades; Cushing's disease shows a preponderance in reproductive-aged women. In children, the condition is uncommon and presents differently, with growth deceleration as a hallmark.[3][6][7]
• Etiology distribution: Among endogenous cases, Cushing's disease accounts for approximately 60–70%, adrenal causes for 20–30%, and ectopic ACTH secretion for 6–10%.[1]

Systemic presentation

The clinical picture is insidious and progressive. No single sign is pathognomonic; diagnosis rests on the simultaneous development of multiple features:[1][6]

• Body habitus: Central weight gain (70–95%), moon facies (81–90%), dorsocervical fat pad ("buffalo hump," ~50%), and supraclavicular fat pad fullness.[4][6]
• Skin: Facial plethora (70–90%), purple striae >1 cm (44–50%), thin skin, easy bruising (35–65%), poor wound healing, acne, hirsutism, and frequent fungal skin infections.[3][4]
• Musculoskeletal: Proximal muscle weakness and atrophy (60–82%), osteopenia/osteoporosis (40–70%), and fragility fractures — vertebral fractures occur in 30–50% of patients.[3][4][8]
• Metabolic/cardiovascular: Hypertension (60–90%), glucose intolerance (45–70%), dyslipidemia, and hypercoagulability.[1][4]
• Neuropsychiatric: Depression, cognitive impairment, insomnia (70–85%).[1][4]

Oral and maxillofacial findings

• Facial changes: Moon facies with mid- and lower-face fat redistribution is the most visible craniofacial manifestation. Facial plethora with telangiectasias is common.[3][6][9]
• Oral mucosal hyperpigmentation: Perioral and buccal mucosal hyperpigmentation occurs in ACTH-dependent forms due to melanocortin receptor stimulation by elevated ACTH. This finding is absent in adrenal Cushing's syndrome, where ACTH is suppressed. In Nelson's syndrome (post-bilateral adrenalectomy), gingival and mucosal hyperpigmentation may be prominent.[4][5][10]
• Oral infections: Immunosuppression predisposes to oral candidiasis and other fungal infections. Bacterial infections may be more severe and protracted.[3][5]
• Wound healing: Impaired collagen synthesis and dermal atrophy lead to poor oral wound healing, a significant concern for surgical procedures.[3][4]
• Periodontal considerations: Glucocorticoid-induced osteoporosis may contribute to alveolar bone loss, and associated diabetes mellitus can exacerbate periodontal disease.[11]
• Pediatric features: In children, Cushing's syndrome causes growth retardation (70–80%) with weight gain, which may affect craniofacial growth and dental development.[4][7]

Cushing's syndrome does not produce a discrete focal jaw lesion. Rather, the radiographic findings reflect generalized glucocorticoid-induced osteoporotic changes throughout the jaws, analogous to those seen in the axial skeleton. Hypercortisolism preferentially affects trabecular bone over cortical bone, and the jaws — particularly the mandible — may show changes detectable on routine dental imaging.[12][13][14]

Location and distribution

• Osteoporotic changes are generalized and bilateral, affecting both the maxilla and mandible.[13][15]
• The mandible is more readily assessed than the maxilla on panoramic radiography due to its cortical anatomy and the availability of validated radiomorphometric indices.[13][16]
• Alveolar bone of both arches may be involved, with the trabecular bone of the mandibular body and ramus being the most studied regions.[17][18]

Internal architecture

• Trabecular rarefaction: The normal trabecular pattern becomes coarsened and sparse, with widened marrow spaces and reduced trabecular number and connectivity. On periapical radiographs, the trabecular pattern may appear more radiolucent with loss of fine trabecular detail.[15][18][19]
• Generalized osteopenia: An overall decrease in radiodensity of the jaws may be appreciated, though this is a subjective finding on conventional radiography and is influenced by exposure parameters.[13][20]
• Fractal dimension analysis and pixel intensity measurements on digital radiographs have shown correlation with reduced bone mineral density in osteoporotic patients, though these are primarily research tools.[18][21]

Periphery and cortical involvement

• Inferior mandibular cortex thinning: The mandibular cortical width (MCW) below the mental foramen is a validated screening parameter. A cortical width ≤3 mm is associated with reduced skeletal bone mineral density.[16][22][23]
• Cortical erosion (Klemetti index): The mandibular cortical index classifies the inferior cortex as normal/smooth (C1), mildly eroded with endosteal lacunar resorption (C2), or heavily eroded with cortical remnants (C3). The presence of C2 or C3 morphology has sensitivity of approximately 0.79 and specificity of 0.56 for detecting reduced BMD. Heavily eroded cortices (C3) combined with fracture risk assessment (FRAX >15%) achieve specificity exceeding 95%.[16][22][24]
• Panoramic mandibular index (PMI): The ratio of cortical width to the distance from the inferior cortex to the inferior border of the mental foramen; a cutoff of 0.3 yields sensitivity and specificity of approximately 0.72 and 0.73, respectively.[16]

Effects on teeth and adjacent structures

• Lamina dura: Thinning or loss of the lamina dura surrounding tooth roots may occur as part of generalized osteoporotic change, though this finding is nonspecific and inconsistently reported.[15]
• Alveolar crest resorption: Generalized alveolar bone loss may be present, particularly when compounded by periodontal disease or diabetes.[11][20]
• Root resorption: Not a recognized feature of Cushing's syndrome.
• Tooth displacement or impaction: Not expected.

Growth pattern and extent

• Changes are diffuse and bilateral rather than expansile or focal.
• The degree of jaw involvement parallels the severity and duration of hypercortisolism. Trabecular bone is affected more markedly than cortical bone, consistent with the known predilection of glucocorticoid-induced osteoporosis for trabecular sites.[3][8][12]

CBCT observations

• CBCT may demonstrate reduced trabecular bone volume and increased marrow space in the mandibular body, providing three-dimensional confirmation of osteoporotic changes that are subtle on two-dimensional imaging.[17]
• Cortical thinning of the inferior mandibular border and mandibular canal walls may be more precisely assessed on CBCT than on panoramic radiography.[17]
• Animal studies of glucocorticoid-treated mandibles show morphological changes in the lacuno-canalicular system and osteocyte apoptosis in alveolar bone on micro-CT, supporting the biological basis for these imaging findings.[14]

MRI — Pituitary evaluation

Pituitary MRI with gadolinium contrast is the primary imaging modality for identifying corticotroph adenomas in Cushing's disease. Approximately 90% are microadenomas.[1] MRI findings guide surgical planning for transsphenoidal adenomectomy.

CT — Adrenal and ectopic tumor localization

Adrenal CT is used to identify cortisol-producing adenomas, adrenal carcinomas, and bilateral adrenal hyperplasia.[1][2] Whole-body CT or functional imaging (PET/CT, octreotide scintigraphy) is employed to localize ectopic ACTH-secreting neuroendocrine tumors, which remain undetected at presentation in 8–19% of cases.[1]

Skeletal assessment

DXA of the lumbar spine and hip is recommended for all patients with Cushing's syndrome to quantify bone mineral density and fracture risk.[8][25] Lateral morphometric imaging of the spine is advised to detect occult vertebral fractures.[25]

The radiographic differential for generalized osteopenia of the jaws encompasses systemic conditions that reduce bone mineral density. The dental radiologist must distinguish Cushing's syndrome from other metabolic and endocrine causes of jaw osteopenia, recognizing that clinical context and biochemical testing — not imaging alone — establish the diagnosis.

The highest-risk diagnostic pitfall is failing to distinguish Cushing's syndrome from primary hyperparathyroidism, as both produce generalized jaw osteopenia and may coexist with secondary hyperparathyroidism in Cushing's syndrome due to altered calcium homeostasis.[3][25] Serum calcium, PTH, and cortisol testing are essential when unexplained generalized jaw osteopenia is identified in a patient with cushingoid features or unexplained metabolic derangements.

Cushing's syndrome does not produce a primary jaw lesion requiring biopsy. The histopathological findings of relevance are those of the causative lesion and the secondary skeletal effects.

Pituitary corticotroph adenoma

• Corticotroph adenomas arise from TPIT-lineage cells of the anterior pituitary and are classified as densely granulated, sparsely granulated, or Crooke cell adenomas based on ACTH expression pattern.[1][32]
• Immunohistochemistry is positive for ACTH and POMC.[33]
• Somatic USP8 mutations are found in 21–60% of corticotroph adenomas.[1][34]

Bone histology

• Glucocorticoid excess produces decreased osteoblast number and function with increased osteoblast and osteocyte apoptosis.[30][35]
• Trabecular thinning and disconnection with increased marrow adiposity are characteristic.[29][35]
• In alveolar bone specifically, animal models demonstrate osteocyte apoptosis and morphological changes in the lacuno-canalicular system.[14]
• Bone formation markers (osteocalcin, alkaline phosphatase) are suppressed, reflecting impaired osteoblast activity.[8][30]

Radiologic-pathologic correlation

The generalized osteopenia seen on dental radiographs corresponds histologically to reduced trabecular bone volume, increased marrow space, and cortical thinning — findings driven by the direct suppressive effects of cortisol on osteoblasts and osteocytes, compounded by indirect effects through hypogonadism, secondary hyperparathyroidism, and growth hormone deficiency.[3][25][29]

Dental management considerations

• Recognition and referral: Dental professionals who identify unexplained generalized jaw osteopenia, particularly in younger patients with cushingoid features (moon facies, facial plethora, striae, easy bruising), should refer for endocrine evaluation. Screening tests include 24-hour urinary free cortisol, late-night salivary cortisol, and 1-mg overnight dexamethasone suppression test.[1][2][6]
• Surgical risk: Impaired wound healing, immunosuppression, hypercoagulability, and uncontrolled hypertension or diabetes increase the risk of oral surgical complications. Elective procedures should ideally be deferred until hypercortisolism is controlled.[4][5]
• Adrenal insufficiency risk: Patients who have undergone treatment for Cushing's syndrome (surgery, medical therapy) may have central adrenal insufficiency requiring stress-dose glucocorticoid supplementation for invasive dental procedures.[1][25]
• Implant considerations: Preclinical data suggest glucocorticoid excess reduces bone-to-implant contact and osseointegration, though limited clinical evidence indicates implant survival may not be significantly affected. Caution is warranted in patients with active uncontrolled hypercortisolism.[36]

Definitive treatment of Cushing's syndrome

• Surgery is first-line for all forms of endogenous Cushing's syndrome:[1][2]
  • Transsphenoidal pituitary adenomectomy for Cushing's disease achieves remission in approximately 80% at specialized centers.[1]
  • Laparoscopic adrenalectomy for unilateral cortisol-producing adenomas.[1]
  • Tumor resection for ectopic ACTH-secreting tumors when localized.[1]
• Medical therapy when surgery fails or is not feasible includes steroidogenesis inhibitors (osilodrostat, ketoconazole, metyrapone), pituitary-targeted agents (pasireotide, cabergoline), and the glucocorticoid receptor antagonist mifepristone.[1][2]
• Radiation therapy and bilateral adrenalectomy are reserved for refractory cases.[1]

Prognosis and bone recovery

• Untreated Cushing's syndrome carries increased mortality from cardiovascular events, thromboembolism, and infection.[2][3]
• After successful treatment, bone mineral density improves substantially, though full recovery may require 4–5 years. Supraphysiological postoperative glucocorticoid replacement may delay bone recovery.[25]
• Recurrence of Cushing's disease occurs in up to 35% of patients after initial surgical remission, necessitating lifelong biochemical surveillance.[1]
• Bisphosphonates with calcium and vitamin D supplementation may accelerate BMD recovery and are recommended for patients with osteoporosis or persistent hypercortisolism.[8][25]

Nelson's syndrome

Following bilateral adrenalectomy for Cushing's disease, loss of cortisol-mediated negative feedback can stimulate growth of the residual pituitary adenoma, producing markedly elevated ACTH levels. The classic presentation includes skin bronzing and mucosal hyperpigmentation — including of the gingivae, buccal mucosa, and scars — due to ACTH-driven melanocortin receptor activation.[10] Modern surveillance protocols have reduced the incidence of this complication.[10]

Pediatric considerations

In children, Cushing's syndrome characteristically presents with weight gain accompanied by growth deceleration (70–80%), a combination that should raise suspicion.[4][7] Chronic hypercortisolism during growth may affect craniofacial development and delay dental eruption. Growth hormone deficiency, which commonly accompanies or follows treatment of Cushing's disease, may compound skeletal effects.[4]

Exogenous glucocorticoid use

The most common cause of Cushing's syndrome encountered in dental practice is iatrogenic, from chronic use of oral, inhaled, injectable, or even topical glucocorticoids.[1] Dental professionals should maintain awareness that patients on long-term corticosteroids may exhibit jaw osteoporotic changes and are at risk for adrenal suppression requiring stress-dose supplementation during invasive procedures.[1][25]