CONGENITAL HYPOPITUITARISM PRESENTING AS ADULT-ONSET HYPOGONADOTROPHIC HYPOGONADISM
SMA Bennett & R Quinton
We present a case of acquired hypogonadotrophic hypogonadism (HH) in a 54-year-old man that illustrates the need for wider endocrine screening in such patients. Having undergone complete pubertal development as a teenager and subsequently fathered two children, the patient presented with a nine-month history of reduced libido, erectile dysfunction, hot sweats and headaches. His GP had diagnosed HH on the basis of a low testosterone with inappropriately low gonadotrophins. Examination was unremarkable, including visual fields and fundoscopy; secondary sexual characteristics were preserved, although testes were relatively small. The differential diagnosis included HH secondary to systemic or local disease, idiopathic HH, or more generalised hypopituitarism.
Baseline investigations: LH & FSH <1.0 units-per-litre, testosterone 2.0 nanomoles-per-litre (NR 9-25), TSH 1.57 milliunits-per-litre (NR 0.3-4.7), freeT4 13 picomoles-per-litre (NR 11-23), IGF-1 7 nanomoles-per-litre (NR 14-32) and prolactin 147 milliunits-per-litre; normal blood count, biochemical profile and ferritin. Magnetic resonance imaging (MRI) revealed a shallow pituitary fossa, containing only a small amount of anterior pituitary tissue, with an ectopic posterior pituitary.
Dynamic pituitary function: short synacthen test - cortisol at 0, 30 & 60 minutes of 271, 574 & 635 nanomoles-per-litre; TRH test - TSH at 0, 20 & 30 minutes of 1.21, 8.44 & 7.64. Circadian TSH values at midnight and 2pm were 1.58 and 1.30 respectively (ratio 1.22).
What first appeared to be isolated idiopathic HH was identified as being a case of acquired hypopituitarism (ACTH sparing). The MRI findings are typical of those seen in congenital hypopituitarism and suggest that the acquired pituitary failure was congenitally programmed. The patient has been started on testosterone and thyroxin replacement therapy. We plan to check his PROP-1 genotype in the future. This case illustrates the importance of adequate pituitary imaging and assessment of anterior pituitary hormones in subjects with acquired HH.