Endocrine Abstracts

Case history: A 24-year-old previously healthy male presented to his GP with unilateral “gynaecomastia”, prompting investigations which showed a low FSH of 0.7 (1–12 IU/l). He had normal libido, erectile function, and a normal sense of smell. He had no children. He was subsequently investigated for persistent dysuria but imaging and cystoscopy were entirely normal. He was a non-smoker who took little alcohol and worked as an insurance agent. His past medical history and family history were unremarkable. Clinical examination revealed a normally androgenized male with no gynaecomastia and normal facial, axillary and pubic hair. His testes were normal in volume and consistency.

Investigations: Unstimulated pituitary hormone tests – (a) FSH – 0.7, 0.8, 0.8 (1–12 IU/l); LH – 1.3, 3.8, 3.3 (1–9 IU/l); (b) 9 am testosterone – 13, 21, 19 (9.7–38.2 nmol/l); (c) prolactin 176, 201 (53–360 mU/l); (d) free T4 14.8 pmol/l, TSH 1.82 mU/l; (e) random cortisol 393 nmol/l; (f) oestradiol 87 (<160 pmol/l); IGF1 – 32.

Semen analysis –

(a) volume 4.3 (>1.4 ml), pH 8.3 (>7.1); (b) sperm concentration 2 (>14.9 million/ml), total sperm/ejaculate 8.6 (38.9 million).

Gonadotrophin releasing hormone test –

Time after GnRH (minutes)

Other tests – (a) plasma inhibin B – 180 pg/l (>80); (b) plasma HCG – <5; Pituitary MRI scan – normal pituitary

FSH beta gene mutation analysis – none identified.

Results and treatment: The above results indicate that this man had isolated FSH deficiency probably of pituitary origin. This lack of FSH has led to poor spermatogenesis and reduction in sperm numbers both absolute and per ejaculate. However, this isolated FSH deficiency does not appear to be due to either a structural hypothalamo-pituitary defect or due to a FSH beta gene mutation.

Conclusion and Points for Discussion: We have presented a man with probable isolated pituitary FSH deficiency. However, the following matters need to be addressed – (a) would gonadotrophin releasing hormone “priming” have increased the FSH response to GnRH?; (b) should clomiphene citrate be given prior to GnRH testing?; (c) is there a need for testicular biopsy?