TSH-STAINING PITUITARY ADENOMAS: RARE, SILENT, AND PLURIHOROMONAL.

Objective: To characterize a single referral center experience with thyroid-stimulating hormone (TSH)-staining adenomas.

Methods: A retrospective chart review was conducted on histopathologic-proven TSH-staining adenomas resected between 2000-2015 at a single center. Tumors were classified as functional (hormonally active) or silent (hormonally inactive). Categorical variables were summarized using counts (n) and percentages; continuous variables were summarized using medians and ranges.

Results: From the 1,065 pituitary adenomas operated, 32 (3.0%) showed diffuse staining for TSH. Median (range) age of patients was 49 years (20 to 77 years), and 21 (66%) were male. Tumor diameter was 20 mm (2 to 37 mm), with 7 (22%) microadenomas and 25 (78%) macroadenomas. Functional tumors (n = 5, 16%) had median diameter of 10 mm (5 to 21 mm) (2 microadenomas). At diagnosis, median (range) TSH was 4.3 μU/mL (1.2 to 6.9 μU/mL), and free thyroxine (FT4) was 2.4 ng/dL (2.1 to 3.4 ng/dL). Three tumors stained for TSH alone, and 2 tumors costained with growth hormone (GH). No cavernous sinus invasion was seen, and 3 (60%) were considered cured after surgery. Silent tumors (n = 27, 84%) had median diameter of 20 mm (2 to 37 mm), with 5 (19%) microadenomas and 22 (81%) macroadenomas. Median (range) TSH was 1.2 μU/mL (0.48 to 4.6 μU/mL), and FT4 was 1.2 ng/dL (0.6 to 1.6). Only 2 (7.4%) tumors stained for TSH alone; the rest were plurihormonal, with GH being the most common. Cavernous sinus invasion was seen in 7 (27%) of the tumors, and 17 (63%) were considered surgically cured.

Conclusion: In our series, 22% of TSH-staining adenomas were microadenomas, and 84% were silent. Most TSH-staining adenomas were plurihormonal, particularly costaining with GH.

Abbreviations: αSU = alpha-subunit; ACTH = adrenocorticotropic hormone; FSH = follicle-stimulating hormone; FT3 = free triiodothyronine; FT4 = free thyroxine; GH = growth hormone; LH = luteinizing hormone; MRI = magnetic resonance imaging; PRL = prolactin; T4 = thyroxine; TSH = thyroid-stimulating hormone.