SUN-290 Pituitary Hyperplasia Due to Uncontrolled Primary Hypothyroidism: Case Series and Literature Review
Authors: Alonso Juan Pablo Godoy , de la Cruz Germán González , Vázquez-Aguirre Marlon Vladimir , Haro Andrea Rocha , Candelario Karla Krystel Ordaz , Cárdenas Romina Flores , Serrano Juanita Silva , Suarez Andrés León , Oliva Luis David Sol , Sámano Miguel Ángel Gómez , Pérez Francisco Javier Gómez , Ramos Daniel Cuevas 
Published: May 2020

Abstract
Background: Pituitary hyperplasia secondary to primary hypothyroidism results from the loss of thyroxine feedback inhibition and the subsequent overproduction of TSH.
Case 1: A 18-year-old female presented with a chronic history of spontaneous galactorrhea, headache and malaise. Autoimmune primary hypothyroidism was diagnosed, with elevated TSH of 490 mIU/L (0.3-5) and low fT4 of 0.33 ng/dL (0.63-1.34). Pituitary MRI showed an enlarged pituitary with compression of the optic chiasm. Hormonal replacement with levothyroxine 75 mcg qd was started. Five months later she was asymptomatic, and normal TSH (1.64 mIU/L) and fT4 (0.9 ng/dL) levels. A new MRI revealed normal size of pituitary gland, with no compression of the optic chiasm and an intact infundibulum.
Case 2: A 24-year-old female with type 1 diabetes and autoimmune primary hypothyroidism, presented with a five-year history of galactorrhea and oligomenorrhea. She was treated with insulin glargine 20U qd, and levothyroxine 200 mcg/day. However, patient’s adherence was bad. She consulted a primary health physician who suspected a prolactinoma after high prolactin levels (77.65, normal 2.64-13.13 ng/mL). Cabergoline was started without any clinical improvement. She then was referred to our service for follow-up. TSH results showed 500 mIU/L, with low fT4 (0.08 ng/dL). Prolactin levels was normal. Pituitary MRI revealed diffuse enlargement of the gland, with compression of infundibulum and optic chiasm. Treatment was modified to levothyroxine/liothyronine 100/20mcg 1 ½ tablet qd. After 7 months, we confirmed normal TSH (0.76 mIU/L) and fT4 (1.23 ng/dL), and the patient was asymptomatic. After 17 months, new MRI showed normal pituitary gland without any compression.
Case 3: A 23-year-old female with a history of Addison′s disease and hypothyroidism diagnosed at age 17 presented with a 6-month history of somnolence, fatigue, headache and amenorrhea. She was previously treated with hydrocortisone 25mg/day, fludrocortisone 0.1mg/day, and levothyroxine 200mcg/day. Patient’s adherence was bad, and multiple hospitalizations because of adrenal crises were reported. Her initial hormonal evaluation revealed high TSH of 460 mIU/L and low fT4 of 0.25 ng/dL, mild hyperprolactinemia (32.16 ng/mL), and very high ACTH levels (2,700 pg/mL, normal 10-100). Pituitary MRI revealed an enlarged pituitary with mild compression of the optic chiasm. Hormonal replacement was modified to fasting levothyroxine alternating 200mcg and 300mcg qd. Her last follow-up showed normal TSH (0.53 mIU/L) and fT4 (1.18 ng/dL) levels. New MRI showed normal pituitary size
Conclusion: We presented three young women, with autoimmune hypothyroidism, who developed pituitary hyperplasia and responded to proper hormonal replacement normalizing pituitary size.
Reference: Endocrinol Diabetes Metab Case Rep. 2015; 2015: 150056.