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Diagnosis of acromegaly and gigantism
Last reviewed: 03.07.2025
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When diagnosing acromegaly, one should take into account the stage of the disease, its phase of activity, as well as the form and features of the course of the pathological process. It is advisable to use X-ray examination data and functional diagnostic methods.
X-ray examination of the skeletal bones reveals periosteal hyperostosis with signs of osteoporosis. The bones of the hands and feet are thickened, their structure is usually preserved. The nail phalanges of the fingers are pagoda-shaped thickened, the nails have a rough, uneven surface. Of the other bone changes in acromegaly, the growth of "spurs" on the heel bones is constant, and somewhat less often on the elbows.
X-ray of the skull reveals true prognathism, divergence of the teeth, enlargement of the occipital protuberance and thickening of the cranial vault. Internal hyperostosis of the frontal bone is often detected. Calcification of the dura mater is noted. The paranasal sinuses, especially the frontal and sphenoid sinuses, are strongly pneumatized, which is also observed in the ethmoid and temporal bones. Proliferation of the air cells of the mammillary processes is noted. In 70-90% of cases, the size of the sella turcica increases. The size of the pituitary tumor in acromegaly depends not so much on the duration of the disease as on the nature and activity of the pathological process, as well as the age at which the disease began. A direct correlation is noted between the size of the sella turcica and the level of somatotropic hormone in the blood and an inverse correlation with the age of the patients. Due to tumor growth, destruction of the walls of the sella turcica is noted. The absence of radiological and ophthalmological signs of a pituitary tumor does not exclude its presence in acromegaly and requires the use of special tomographic research methods.
The rib cage is deformed, barrel-shaped with widened intercostal spaces. Kyphoscoliosis develops. The spine is characterized by the disappearance of the "waist" in the ventral sections of the thoracic vertebrae, multiple contours with the superposition of newly formed bone on the old, beak-shaped protrusions and paravertebral arthrosis are observed. The joints are often deformed with a limitation of their function. The phenomena of deforming arthrosis are most pronounced in large joints.
The thickness of soft tissues on the plantar surface of the feet in patients exceeds 22 mm and directly correlates with the levels of STH and IGF-1. This test can be used to determine the activity of acromegaly and dynamically assess the adequacy of the therapy.
Laboratory methods of research in acromegaly reveal the following changes in somatotropic function: disturbance of physiological secretion of somatotropic hormone, manifested by paradoxical increase in growth hormone content in response to glucose load, intravenous administration of thyroliberin, luliberin, no increase in somatotropic hormone level is observed during sleep; paradoxical decrease in somatotropic hormone level is revealed during insulin hypoglycemia test, administration of arginine, L-dopa, dopamine, bromocriptine (parlodel), as well as during physical activity.
The most common tests that allow assessing the state of the hypothalamic-pituitary system in acromegaly and the integrity of feedback mechanisms include the oral glucose tolerance test and the insulin hypoglycemia test. If, under normal conditions, taking 1.75 g of glucose per 1 kg of body weight leads to a significant decrease in the level of somatotropic hormone in the blood, then in acromegaly there is either no reaction/decrease in somatotropic hormone below 2 ng/ml for 2-3 hours, or a paradoxical increase in the level of growth hormone.
The introduction of insulin at a dose of 0.25 U per 1 kg of body weight in the norm, leading to hypoglycemia, contributes to an increase in the content of growth hormone in the blood serum with a maximum at 30-60 min. In acromegaly, depending on the value of the initial level of somatotropic hormone, hyporeactive, areactive and paradoxical reactions are detected. The latter is manifested by a decrease in the level of somatotropic hormone in the blood serum.
The most characteristic changes that allow their use for diagnostic purposes are manifested at the pituitary level. The formation of a pituitary adenoma promotes the formation of less differentiated somatotrophs with an altered receptor apparatus. As a result, tumor cells acquire the ability to respond by increasing somatotropic secretion in response to the action of stimuli that are non-specific for a given type of cell. Thus, hypothalamic releasing factors (luliberin, thyroliberin), without normally affecting the production of somatotropic hormone, activate somatotropic secretion in approximately 20-60% of patients with acromegaly.
To establish this phenomenon, thyroliberin is administered intravenously at a dose of 200 mcg, followed by blood sampling every 15 minutes for 90-120 minutes. The presence of altered sensitivity to thyroliberin, determined by an increase in the level of somatotropic hormone by 100% or more from the initial level, is a sign indicating a violation of the receptor activity of somatotrophs and pathognomonic for a pituitary tumor. However, when finally establishing a diagnosis, it should be taken into account that a similar nonspecific increase in the STH level in response to the administration of thyroliberin can also be observed in some pathological conditions (depressive syndrome, nervous anorexia, primary hypothyroidism, renal failure). In diagnosing a tumor process in the pituitary gland, an additional study of the secretion of prolactin and TSH in response to the administration of thyroliberin may be of certain value. A blocked or delayed response of these hormones may indirectly indicate a pituitary tumor.
In clinical practice, a functional test with L-dopa, a stimulator of dopaminergic receptors, has become widespread. Taking the drug in a dose of 0.5 g orally during the active phase of acromegaly does not lead to an increase, as is observed in the norm, but to a paradoxical activity of the hypothalamic-pituitary system. Normalization of this reaction during treatment is a criterion for the rationality of the therapy.
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