Acromegaly

Acromegaly is a chronic, slowly progressive systemic disorder caused by sustained hypersecretion of growth hormone (GH) and the consequent elevation of insulin-like growth factor 1 (IGF-1), in more than 95% of cases arising from a benign GH-secreting somatotroph adenoma of the pituitary.[1][2] When GH excess begins after epiphyseal closure, the skeletal response is appositional rather than linear, producing the characteristic acral and craniofacial overgrowth; onset before closure instead produces gigantism.[3] The jaws and facial skeleton are among the earliest and most visible sites of involvement, and the resulting phenotype is frequently encountered in dental settings before an endocrine diagnosis is made.[4][5]

The signature maxillofacial pattern is disproportionate mandibular overgrowth with condylar-driven ramus elongation, producing prognathism, an anterior open bite with Class III relationship, generalized interdental spacing, and macroglossia.[4][6] Management is directed at the underlying adenoma—biochemical control through surgery, medical therapy, or radiotherapy—with orthognathic and prosthodontic rehabilitation reserved for residual deformity.[7][8]

The term "acromegaly" (enlargement of the extremities) was introduced by Pierre Marie in 1886; earlier descriptors such as "macrosomia" and "prosopectasia" are obsolete and appear only historically.[3] The condition is defined by GH/IGF-1 excess in the skeletally mature patient and is distinguished from pituitary gigantism, in which the same hormonal excess predates epiphyseal fusion.[3] Underlying somatotroph tumors are classified pathologically as densely or sparsely granulated, with mammosomatotroph and mixed GH–prolactin tumors also recognized. "Acromegaly" denotes the clinical syndrome, not a discrete jaw lesion; the maxillofacial findings described here are secondary skeletal manifestations of that syndrome.[2]

Acromegaly is rare, with reported prevalence of roughly 28–137 cases per million and annual incidence of approximately 2–11 per million.[1][9][10] It is diagnosed most often between 40 and 47 years of age, affecting both sexes.[9] Because features evolve insidiously, diagnosis is typically delayed 5–10 years from symptom onset, among the longest delays in endocrinology, although wider imaging access has shortened this in some series.[4][9]

Oro-dental and craniofacial changes are common at presentation rather than incidental. In pooled data, facial features are present in about 65% of patients and oral changes in about 62% at diagnosis.[12] Reported frequencies for individual oral signs include macroglossia in 54–59% and interdental spacing/diastema in 40–62%.[6][12] Within the facial skeleton, the mandible is consistently the most severely and disproportionately affected site.[13]

Presentation reflects decades of soft-tissue and skeletal overgrowth. Patients commonly report increasing ring, glove, or shoe size, coarsening facies, frontal bossing, and enlargement of the nose and lips, often noticed by others before the patient.[1][10] Physical changes—especially dysmorphic facies—are a leading reason patients seek care.[1]

Maxillofacial and oral complaints are frequently the first presentation to a clinician and carry diagnostic weight:

• Progressive malocclusion and bite change in an adult, with newly developing anterior spacing, a widening jaw, and difficulty with previously well-fitting dentures.[4][14]
• Mandibular prognathism and facial elongation, with incisor separation and Class III occlusion.[7][10]
• Macroglossia, often with scalloped lateral tongue margins, slurred or deepened speech, and contribution to obstructive sleep apnea.[4][15]
• Temporomandibular symptoms, including joint pain, clicking, and altered loading from condylar remodeling.[6][15]

The tempo is characteristically slow and insidious, which both delays recognition and accounts for the advanced skeletal remodeling often present at diagnosis.[9] Red flags warranting urgent endocrine referral include headache, visual field loss from suprasellar extension, and the systemic comorbidities of GH excess—hypertension, diabetes, cardiomyopathy, thyroid enlargement, and sleep apnea.[1][10] Dental practitioners occupy a front-line screening role, yet referral for suspected acromegaly remains uncommon.[5]

The dental and maxillofacial radiographic picture is one of disproportionate skeletal enlargement and remodeling superimposed on an otherwise normal bone architecture, without a destructive or neoplastic focus.

Location and distribution

Changes are generalized across the craniofacial skeleton but are most pronounced in the mandible.[13] The mandible enlarges disproportionately relative to the maxilla, and the imbalance between maxillary and mandibular projection underlies the Class III skeletal pattern.[13][16] Measured mandibular length and overall mandibular volume are increased relative to controls, whereas maxillary length shows little or no consistent increase.[16]

Shape and growth pattern

Growth is appositional and condylar-driven: reactivation of condylar growth centers with periosteal bone apposition produces slow, progressive enlargement rather than expansile ballooning.[4] The ascending ramus elongates more than the mandibular body, and the gonial (mandibular) angle becomes more obtuse, increasing anterior and posterior facial height.[13][17] The overall mandibular contour is altered in shape, not merely enlarged.[13]

Periphery and internal architecture

The jaws retain a corticated, non-aggressive periphery; there is no lytic internal lesion, moth-eaten pattern, or soft-tissue mass. Internal trabecular architecture is preserved, with generalized enlargement rather than focal rarefaction or sclerosis. Cortical outlines remain intact, consistent with remodeling rather than invasion.

Effects on teeth and the alveolar process

• Interdental spacing (diastemata) from arch enlargement outpacing fixed tooth size, producing generalized spacing most evident anteriorly.[4][6]
• Buccal/labial tipping of mandibular teeth attributed to macroglossia and tongue pressure.[4]
• Hypercementosis has been described but is an inconsistent, lower-frequency finding and should not be considered characteristic.

Effects on adjacent structures

• Sella turcica enlargement, reflecting the underlying adenoma, is a recognized incidental finding on lateral skull projections and a cue for systemic disease.[5][13]
• Paranasal sinus and frontal bone changes: enlargement of the frontal sinus and increased sphenoidal and maxillary sinus dimensions, with protrusion of the supraorbital ridges and thickening of the frontal bones.[6][13][18]
• Cranial vault thickening and increased anteroposterior skull diameter are described, the latter correlating with GH/IGF-1 levels.[18]
• Pharyngeal airway narrowing with an elongated, thickened soft palate and a more inferiorly positioned hyoid.[13][19]

Extent and variants

Involvement is bilateral and symmetric in the typical case. A recognized variant is asymmetric condylar hyperplasia, producing a unilateral lateral prominence and asymmetric mandibular growth that can mimic a primary condylar lesion.[20] Cephalometric parameters do not reliably distinguish biochemically active from controlled disease, so radiographic severity reflects cumulative exposure rather than current activity.[13]

Sellar and pituitary imaging

Once acromegaly is confirmed biochemically, dedicated pituitary magnetic resonance imaging is the study of choice to define the adenoma, its size, and parasellar extension; computed tomography is reserved for when magnetic resonance is contraindicated.[2] Approximately 70% of patients harbor a macroadenoma at diagnosis, frequently with cavernous sinus extension, which directly influences surgical planning and the likelihood of biochemical remission.[1][21] Formal visual field testing is indicated when the tumor abuts the optic chiasm.[2] This finding materially changes staging and management and is not obtainable from dental imaging.

Most diagnostic confusion arises when mandibular overgrowth, prognathism, or macroglossia is attributed to a local or developmental cause, missing the systemic driver. The highest-yield distinction is recognizing the combination of adult-onset progressive jaw change with acral and facial coarsening and prompting IGF-1 testing.

The dominant pitfall is framing an adult's new prognathism, diastemata, and denture misfit as isolated orthodontic or prosthodontic problems; a single age-adjusted serum IGF-1 is the decisive next step, confirmed when necessary by failure of GH suppression during an oral glucose load.[2][22]

The craniofacial changes themselves are not a biopsy target; diagnostic histopathology concerns the causative somatotroph adenoma. Tumors are classified as densely granulated (smaller, more biochemically active, older patients) or sparsely granulated (younger patients, more aggressive, often less responsive to first-generation somatostatin ligands), with mammosomatotroph and mixed GH–prolactin tumors also recognized.[2][10] Immunohistochemical GH positivity, cytokeratin granulation pattern, and somatostatin receptor subtype 2 expression inform both classification and predicted response to medical therapy.[2]

Radiologic-pathologic correlation of the jaws reflects endochondral and periosteal mechanisms rather than a tumor: reactivation of condylar cartilage growth and periosteal apposition explain ramus elongation, the obtuse gonial angle, and generalized cortical thickening seen on imaging.[4][13] At the molecular level, somatic GNAS (Gsα) mutations are present in a substantial proportion of sporadic somatotroph adenomas, and germline contexts include AIP mutations, multiple endocrine neoplasia types 1 and 4, and Carney complex, and postzygotic mosaic GNAS mutation causes McCune–Albright syndrome; these affect tumor behavior and screening rather than the appearance of the jaw lesion.[2][3]

Workup begins with age-adjusted serum IGF-1 as the single best screening test; random GH is unreliable because of pulsatile secretion.[1][2] Equivocal or discordant results are confirmed by lack of GH suppression (nadir below the assay-specific threshold, historically under 1 µg/L) during a 75-g oral glucose tolerance test.[2][23] Biochemical confirmation is followed by pituitary imaging and visual field testing when indicated, and referral to a multidisciplinary pituitary center.[2][21]

Definitive treatment targets the adenoma:

• Transsphenoidal surgery is first-line, achieving remission in roughly 78% of microadenomas but only about 41–53% of macroadenomas; large size, high preoperative GH, and cavernous sinus invasion reduce success.[7][8][21]
• Medical therapy is used for persistent or recurrent disease, or when surgery is unsuitable: first-generation somatostatin receptor ligands (octreotide, lanreotide, oral octreotide), pasireotide, the GH-receptor antagonist pegvisomant, and cabergoline in milder elevations. Pasireotide carries a notable risk of hyperglycemia (reported in roughly 57–74%), and pegvisomant does not reduce tumor size.[7][8]
• Radiotherapy, increasingly stereotactic, is generally third-line for refractory disease.[8][24]

Biochemical remission is defined by a normalized age-adjusted IGF-1 with suppressed GH, reassessed roughly 12 weeks to 6 months postoperatively; the 5-year recurrence rate after apparent surgical cure is approximately 2–8%.[8][21] Achieving control normalizes the otherwise elevated mortality.[21]

For the maxillofacial component, established bony deformity does not regress with treatment of the endocrine disease, whereas soft-tissue changes including macroglossia improve more consistently.[6][14] Orthognathic surgery and prosthodontic rehabilitation are considered for residual malocclusion and function once disease is biochemically controlled, with care taken regarding airway and anesthetic risk from sleep apnea and craniofacial changes.[14][17] Dental surveillance remains important for periodontal disease, prosthetic fit, and monitoring of persistent or progressive changes.[14]