Mr CB is a 28 year old man who was known to the endocrine service for management of type 1 diabetes mellitus and Hashimoto’s thyroiditis, newly diagnosed less than 12 months prior. His diabetes was well controlled on basal bolus insulin, with HBA1C 5.8%. He was on thyroxine 50mcg and was clinically and biochemically euthyroid. He attended routine follow up and mentioned that his wife and he were trying to conceive for the last 3 months. Neither partner had any previous children. His GP had performed a semen analysis which demonstrated azoospermia. His developmental history was unremarkable, without any history of mumps, testicular trauma or cryptorchidism, no history of hormone therapy or anabolic steroid use. He denied any decreased libido, with otherwise normal sexual function. On examination he was noted to have a BMI of 38. He had no scrotal or penile malformations, with bilateral small testes measuring 8mL on volume. He had a normal male pattern of hair growth, normal arm span to height ratio, no gynaecomastia or signs of pituitary disease. Further investigations revealed consistently elevated FSH levels between 12-13.6IU/L (1.0-12), normal LH levels between 3.2-4.6IU/L (0.6-12) and low testosterone levels between 5.9-9.6mmol/L (11.5-32). Anti-sperm antibodies were negative and chromosomal studies revealed 46XY karyotype. He underwent a testicular biopsy, which revealed the presence of sertoli cell only syndrome.
Sertoli cell only syndrome is a rare histologic diagnosis where seminiferous tubules are devoid of germ cells and are lined with only sertoli cells. They present with infertility, normal androgenisation, small testes, azoospermia, normal testosterone and LH levels with selectively elevated FSH levels. Inhibin B is secreted by sertoli cells in response to FSH stimulation. In sertoli cell only syndrome inhibin B levels are low, reflecting the absence of germ cells and implying a measure of sertoli cell dysfunction.