Poster Presentation ESA-SRB 2023 in conjunction with ENSA

Resolution of pituitary ‘macroadenoma’ from treatment of underlying severe primary hypothyroidism (#339)

Arunan Sriravindrarajah 1 2 3 4 , Christina Lee 1 , Kirby Wong 1 , Anne Maree Kean 1
  1. Royal Prince Alfred Hospital, Sydney, NSW, Australia
  2. St Vincent’s Hospital, Sydney, NSW, Australia
  3. Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia
  4. Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia

The hypothalamic-pituitary-thyroid axis plays an important role in the regulation of normal thyroid function. Untreated primary hypothyroidism will lead to the loss of thyroxine inhibition on the hypothalamus, resulting in elevated thyrotophin-releasing hormone and possible hyperplasia of thyrotroph and / or lactotroph cells in the anterior pituitary[1].

 

A 52-year-old male presented with dizziness and nausea on a background of childhood hypothyroidism with total thyroidectomy at age 19. MRI pituitary demonstrated a 15x15x15mm sellar mass inseparable from the pituitary gland with suprasellar extension contacting and mildly displacing the optic chiasm. Biochemical investigations demonstrated severe primary hypothyroidism with TSH >99mIU/L (0.27-4.2), FT4 0.7pmol/L (12-25), FT3 1.1pmol/L (2.5-6.0) and secondary hypogonadism with FSH 6.6IU/L (1.5-12.4), LH 2.2IU/L (1.7-8.6) and testosterone 3.8nmol/L (10-30). The remainder of the pituitary panel was within normal range with cortisol (0835) 261nmol/L (170-500), ACTH 3.4pmol/L (<=10), prolactin 12.1ng/mL (2-16) and IGF-1 17.1nmol/L (7.2-25.5). He was commenced on levothyroxine 200mcg daily with repeat pathology after 6 months demonstrating biochemical euthyroidism with TSH 3.86mIU/L, FT4 16.8pmol/L, FT3 4.3pmol/L. His hypothalamic-gonadotrophic axis also normalised with FSH 5.9IU/L, LH 5.1IU/L and testosterone 19.3nmol/L. Repeat MRI pituitary showed an interval decrease in the size of the sellar mass to 15x15x8mm and no further contact or displacement of the optic chiasm. There were no clinical or radiological features at the time to suggest pituitary apoplexy. Multiple further surveillance MRI pituitary over the next 3 years showed a normal sized pituitary gland with the superior to inferior dimension of the gland gradually decreasing to 7mm. He remained biochemically euthyroid during this period.

 

This case demonstrates severe primary hypothyroidism may present with pituitary hyperplasia that may mimic a pituitary adenoma. Treatment with thyroid hormone replacement and subsequent normalisation of TSH levels would be expected to result in a decrease in the size of the pituitary enlargement.

  1. Feldt-Rasmussen, U., Effraimidis, G. and Klose, M. The hypothalamus-pituitary-thyroid (HPT)-axis and its role in physiology and pathophysiology of other hypothalamus-pituitary functions. Mol Cell Endocrinol. 2021;525:111173