TSH-secreting pituitary adenoma
A TSH-secreting pituitary adenoma is an extremely rare thyrotroph tumor that autonomously secretes thyroid-stimulating hormone, causing hyperthyroidism with elevated free thyroxine and triiodothyronine but an inappropriately normal or elevated TSH. Transsphenoidal resection of the tumor is the treatment of choice, with somatostatin analogue therapy such as octreotide used to control hyperthyroidism before surgery or when surgery is not feasible.
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What this article covers
- Overview
Definition: a TSH-secreting pituitary adenoma is a thyrotroph-derived pituitary tumor that autonomously secretes thyroid-stimulating hormone (TSH), driving hyperthyroidism independent of normal hypothalamic-pituitary-thyroid feedback.
- Epidemiology
One of the rarest functioning pituitary tumor types: TSH-secreting pituitary tumors are extremely rare among all pituitary adenomas.
- Risk factors
Any pituitary tumor substrate: as with other functioning pituitary adenomas, a TSH-secreting tumor arises from clonal expansion of thyrotroph cells in the anterior pituitary; no specific predisposing…
- Pathophysiology
Thyrotroph cells normally release TSH under stimulation by hypothalamic thyrotropin-releasing hormone, and TSH in turn drives thyroid follicular cells to synthesize and release T4 and T3.
- Clinical features
Symptoms of hyperthyroidism: heat intolerance, palpitations, nervousness, irritability, and insomnia.
- Differential diagnosis
Graves disease: hyperthyroidism with a suppressed TSH, diffuse radioactive iodine uptake, and thyrotropin receptor antibodies, unlike the non-suppressed TSH of a TSH-secreting tumor.
- Diagnosis
The diagnosis is established by the combination of elevated free T4 and T3 with an inappropriately normal or frankly elevated TSH, after thyroid assay interference, TSH resistance, and familial…
- Management
First, for a surgically resectable tumor, transsphenoidal resection is the treatment of choice, the standard surgical approach for pituitary tumors through the nares or mouth.
- Complications
Thyroid storm: life-threatening hyperthyroidism with multisystem decompensation if the underlying TSH excess goes unrecognized or uncontrolled.
- Prognosis
Favorable when the tumor is fully resected: transsphenoidal surgery is the treatment of choice and directly addresses the source of TSH excess.
- Prevention
Do not attribute an elevated free T4 with a non-suppressed TSH to laboratory error without first excluding biotin interference (discontinue biotin at least 12 hours before repeat testing) and…
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Related articles
- Hyperthyroidism
Hyperthyroidism is the clinical syndrome of thyroid hormone excess, produced by a range of causes from Graves disease and autonomously functioning nodules to destructive thyroiditis and exogenous hormone ingestion. Diagnosis begins with a suppressed thyroid-stimulating hormone and elevated free thyroxine, followed by radioactive iodine uptake testing or antibody measurement to identify the cause, and first-line treatment is a beta blocker for symptom control while the underlying cause directs thionamide, radioactive iodine ablation, or thyroidectomy therapy.
- Graves disease
Graves disease is an autoimmune disorder in which thyrotropin receptor antibodies stimulate the thyroid, causing hyperthyroidism, and is the most common cause of thyrotoxicosis in iodine-sufficient regions. Diagnosis rests on a suppressed thyroid-stimulating hormone with elevated free thyroxine and positive thyrotropin receptor antibodies, and first-line treatment is a thionamide, most often methimazole, with radioactive iodine or thyroidectomy reserved for recurrence or patient preference.
- Nonfunctioning pituitary adenoma
A nonfunctioning pituitary adenoma is a benign pituitary tumor, usually of gonadotroph origin, that does not secrete a clinically excessive hormone and presents through mass effect (visual field loss, headache) or hypopituitarism rather than a hypersecretory syndrome. Diagnosis requires excluding hormone excess and screening for hypopituitarism; treatment is observation for a small asymptomatic incidentaloma or transsphenoidal surgery for mass effect, apoplexy, or growth on follow-up.