U029

Thyroxine replacement and adrenal insufficiency.

Dr. Bijal Patel, and Dr. Sithara Perera

Maidstone and Tunbridge Wells NHS Trust.

Case History:

A 72 year old female was admitted to hospital in May 2014 generally unwell and lethargic, and was noted to have a Na level of 122 mmol/L. She was otherwise fit and well, with a background of hypothyroidism (diagnosed 2013) on thyroxine replacement.

Subsequent inpatient investigations revealed: 9am cortisol 11 nmol/L, ACTH <5, TSH 0.5, FT4 11.1, FT3 3.2, LH<0.1, FSH<2.0, Prolactin 375, IGF- 1 <3.3. MRI pituitary showed a 10mm calcified sellar and suprasellar lesion. The case was referred to King’s pituitary MDT and a diagnosis of anterior hypopituitarism secondary to a likely craniopharyngioma was made.

The patient was promptly commenced on hydrocortisone, her levothyroxine doses were adjusted and she is currently considering growth hormone replacement. Conservative management and image surveillance is planned for the craniopharyngioma. She improved symptomatically and her Na level returned to 133mmol/L and cortisol 790 nmol/L.

Learning Point:

It is well known treating hypothyroidism prior to hypoadrenalism can precipitate a fatal adrenal crisis. This occurs as thyroid hormones increase both cortisol clearance and cortisol requirement through a raised metabolic rate. The patient’s recent thyroxine replacement has likely exacerbated her adrenal insufficiency, leading to this admission.  This case demonstrates the importance of performing a full pituitary profile in the context of non-specific symptoms and secondary hypothyroidism.