Time Bound Regression of Pituitary Hyperplasia in Primary Pituitary Hypothyroidism Following Treatment

Aim: The aim was to prospectively study radiological regression of pituitary hyperplasia following the treatment for primary hypothyroidism by serial magnetic resonance imaging (MRI). Subjects and Methods: Seven patients (1 male and 6 females) with profound hypothyroidism were included, age ranging from 13 to 42 years. MRI for pituitary was done at first visit and on follow‑up. Pituitary size on imaging was matched with baseline T3, T4, thyroid-stimulating hormone (TSH), and thyroid peroxidase antibody antibodies and TSH on follow-up. Results: By 6 weeks all patients showed clinical improvement with near normalization of thyroid function tests in most patients. The TSH normalization was well correlated with regression of the pituitary enlargement on imaging at 6 weeks. The height of pituitary gland at baseline was 13.24 ± 3.61 mm, at first follow‑up 9.68 ± 1.32 mm, and at second follow‑up 7.80 ± 3.95 mm. The diameter of the pituitary gland at baseline was 14.47 ± 4.14 mm, at first follow‑up 11.83 ± 3.99 mm, and at second follow‑up 7.25 ± 4.59 mm. The height of the pituitary gland significantly reduced in first and second follow‑up (P < 0.05) and reduction in diameter on second follow-up (P < 0.05). Conclusion: Pituitary hyperplasia secondary to primary hypothyroidism regresses with treatment within 6 weeks of initiation of treatment in its height however, it takes months for reduction in the diameter of the gland. We recommend repeat imaging in enlarged and homogenously enhancing pituitary gland in patients of primary hypothyroidism at 6 weeks of initiation of treatment to prove or disprove hyperplasia.